First, there was a boom that some thought was an explosion. Then came the rush of escaping natural gas that sounded like a jet engine. Finally there were the sirens and shouts of rescuers searching for survivors.

A little over a week has passed since the Fern Hollow Bridge collapsed, sending a pickup truck, four cars and a Port Authority Bus into a ravine in Frick Park and leaving 10 people injured.

Now, the noise will be made by the National Transportation Safety Board, which is investigating to determine what happened. The board’s preliminary report was released on Feb. 7. At the same time, city, county and state officials are trying to explain to a nervous public how the City of Bridges will maintain its other aging structures.

But with so much talk about the future, another facet of the traumatic event was the collaborative spirit that emerged from the chaos of that chilly Friday morning. when firefighters, emergency medical services, police officers, the city government, business owners, neighbors — and even the president of the United States — came together in Point Breeze.

In a minute-by-minute timeline, the Pittsburgh Post-Gazette has reconstructed the events of Jan. 28 through multiple eyewitness accounts to get a better idea of what transpired.

About 6:40 a.m.

Initial access and victim search take place early Friday morning at the location of the Fern Hollow Bridge collapse in Frick Park. (Pittsburgh Bureau of Police Officer Tyler Nestler)

Point Breeze residents report hearing a “loud boom,” presumably the Fern Hollow Bridge collapsing.

“There was a boom, then a monster sound,” says Point Breeze resident Melissa Bakth. “It was so loud, and it didn’t stop. It could’ve been me. I’m on that bridge every day. It’s very, very busy.”

About the same time, Allegheny County 911 dispatchers receive a call about the bridge over Nine Mile Run in Frick Park.

“A lot of screaming and static on the phone” a 911 dispatcher tells first responders. “Possibly off a bridge, saying the bridge fully gave out. Unknown injuries.”

“We are getting multiple calls that part of the bridge may have collapsed,” another dispatcher radios.

6:50 a.m.

Emergency crews on the scene of a bridge collapse at Forbes and Braddock Avenues. (Pittsburgh Public Safety)

Pittsburgh Public Safety advises commuters to avoid the intersection of Forbes and South Braddock avenues and says police, fire and EMS personnel are arriving on scene.

“The bridge has collapsed, and they’ve got persons on their bus” a first responder says in a 911 dispatch.

“We get calls all the time for things that sound sort of unbelievable, and you try to get your bearings together and say, ‘Is that what I just heard?’” says Pittsburgh EMS District Chief Antwain Carter, who responded that morning. “And it was one of them.”

“I make my way downstairs, get in my vehicle,” recalls Chief Carter, who had started his shift less than an hour beforehand. “That morning it had snowed, a little bit of light snow, [and] the roads were a little bit slick. The weather condition wasn’t optimal. I rolled out of EMS headquarters, did sort of a hook slide, started down, and the reports were coming in from credible sources.

“That’s when the full alarm for a mass casualty was put in.”

6:59 a.m. Pittsburgh Public Safety warns of a “strong smell of natural gas” in the area of the bridge. It came from a natural gas line on Forbes Avenue near Dallas Avenue, ruptured during the collapse.

“As I unlocked the front door, the wave of natural gas hit the building,” says Robert Randozzo, manager of Frick Park Automotive on South Braddock Avenue near the bridge. “A heavy, heavy smell.”

“It was so loud, and it didn’t stop,” Ms. Bakth says of the roar of gas flowing out of the pipe. A responding firefighter says it sounded like a “jet engine.”

7:15 a.m. Pittsburgh City Councilman Corey O’Connor, whose district contains Frick Park, arrives.

Mr. O’Connor had driven that bridge “thousands of times” and played Little League baseball at a field nearby, he tells the Post-Gazette. Knowing “the amount of traffic we have on that bridge,” he worried about casualties.

Mr. O’Connor recalls that residents had told him homeless people sometimes used the bridge for shelter. He is briefed by public safety officials.

Shortly after 7:30 a.m. Pittsburgh Fire Chief Darryl Jones arrives.

“I was preparing myself to deal with not only mass casualties but mass fatalities as well,” Chief Jones says.

He could smell the leaking natural gas. He walked up to Chief Carter, who was in command, and asked for a briefing. They then worked to set up a unified command.

7:50 a.m. Pittsburgh Public Safety confirms the ruptured gas line has been turned off

“It wasn’t like a train whistle, but the break — you could hear it,” Chief Carter says.

“That pipe had to be enormous,” he continues. “That’s the first thing that goes through any responder’s mind, ‘scene safety.’ That threw a red flag. If there was a spark — I’m not a chemist — but as much as I say I was fearful, I was also fearful of failure. There was no room for failure that day.”

Around 8:30 a.m. Pittsburgh Mayor Ed Gainey is on his way to the bridge

A few minutes later

Pittsburgh fire chief Darryl Jones speaks next to mayor Ed Gainey on the scene of a bridge collapse. (Matt Freed/Post-Gazette)

Mr. Gainey and Chief Jones tell reporters that 10 people are injured, and three were taken to a hospital.

“The good thing, at this point, is that there’s no fatalities,” Mr. Gainey tells the gathered news media.

Daryl Luciani, the Port Authority driver who was operating the 61B bus when it fell with the bridge, says later in a radio interview that a firefighter and a police officer with flashlights came through the woods to reach the bottom of the ravine.

Mr. Luciani feared that his bus, caught at an angle on the collapsed bridge deck, was going to slide backward into the ravine. But rescuers were able to crawl to the articulated vehicle and help him and two passengers out. They went up a ladder to safety.

In a tweet about the same time, the mayor writes:

“Today a bridge collapsed near Forbes and S Braddock. I am thankful there are no reported fatalities or critical injuries at this time. Thank you @PghPublicSafety for the quick response and thank you to the county, state, and federal governments for the cooperation and assistance.”

Chief Carter’s EMS team was one of several that climbed into the ravine to assist motorists.

“Two of them had more significant injuries, where they were going to need to be extricated out of there,” he says. “That’s where the resources came into play.”

Chief Jones says during a press briefing that the bridge did not fall suddenly; the vehicles rolled down the tilted deck toward the bottom of the ravine.

Chief Jones and Chief Carter talk about what the scene would have been like had the bridge collapsed a half hour later — or had the city school district not been on a two-hour delay because of the weather. It would have been “a different story,” Chief Jones says.

Besides rappelling 150 feet into the the ravine, some rescuers make a literal human chain, linking their arms together to help pull to safety victims trapped in their vehicles.

“It was a combined effort from fire, EMS, law enforcement, and it was all orchestrated and held in glue by the county communications center,” Mr. Carter says. “Everybody played an important part in this chain of survival.”

8:45 a.m. Mr. Biden, on his way to Pittsburgh to talk about his infrastructure plan, is briefed on the collapse.

White House Press Secretary Jen Psaki says in a tweet:

“@POTUS has been told of the bridge collapse in Pittsburgh. Our team is in touch with state and local officials on the ground as they continue to gather information about the cause of the collapse.”

Around 8:55 a.m. UPMC Presbyterian announces it is treating three patients from the collapse.
About 9 a.m.

Mayor Ed Gainey and Allegheny County Executive Rich Fitzgerald. (Matt Freed/Post-Gazette)

Allegheny County Executive Rich Fitzgerald tells reporters that it would take at least a year for the bridge to be replaced.

“It does highlight the needs of what we have here in this region,” Mr. Fitzgerald says. “I think it’ll also show a spotlight on how often bridge inspections are done, weight limits, all the type of things that we know need to be done, and because there hasn’t been money over the years, we’ve deferred a lot of things that need to be done.”

In a tweet, he shares photos of the crumbled bridge, writing:

“We are extremely fortunate there there were only non-life threatening injuries in this morning’s partial bridge collapse. Thank you to all of our first responders for their quick action. This is a major artery, and we have a lot of work ahead of us.”

9 a.m. Red Cross workers arrive to assist.

10:45 a.m. The National Transportation Safety Board dispatches an investigative team that includes board chairwoman Jennifer Homendy.

“It’s our job to figure out what happened, why it happened and to prevent it from happening again,” she tells reporters later. “Over the coming weeks we are going to put this bridge under a microscope.”

11:15 a.m. The Pennsylvania Urban Search and Rescue team arrives.

11:20 a.m. Public safety officials close Frick Park.

“It’s funny Biden’s in town on the infrastructure bill,” says John Jacobs, a Squirrel Hill resident who usually walks his dogs in the park. “What a coincidence.”

“It’s remarkable — I never imagined this thing would collapse,” says Jay Duque-Chavez, who had walked to the park from his home in Squirrel Hill. “Now it’s like the outlook on life around this is going to be different going forward — going over, going underneath. I was driving just yesterday around 8:30, then less than 24 hours, you go back to see this.”

11:30 a.m. UPMC Shadyside announces it is treating a bridge casualty for minor injuries.

11:37 a.m.The mayor wraps up a phone conversation with Mr. Biden, who is on his way to the scene.

In a tweet, Mr. Gainey writes: “Thank you @POTUS for your support as we address the Fern Hollow Bridge collapse. I look forward to seeing you soon.”

12:44 p.m.

President Joe Biden arrives at Allegheny County Airport in West Mifflin. (Emily Matthews/Post-Gazette)

Air Force One touches down at Allegheny County Airport

1:15 p.m.

The motorcade for President Joe Biden moves along Forbes Ave. (Stephanie Strasburg/Post-Gazette)

Mr. Biden arrives, stopping on the Squirrel Hill side of the bridge to meet with Mr. Gainey, other public officials, and first responders.

“These guys deserve an incredible amount of credit going down here,” Mr. Biden says, shaking hands with first responders.

“We’re going to fix them all,” Mr. Biden says of the city’s bridges. “We’re sending the money.”

President Biden talks with Mayor Ed Gainey at the site of the bridge collapse. (Saul Loeb/AFP via Getty Images)

In a tweet, the president writes: “This morning, the Frick Park Bridge collapsed in Pittsburgh. This afternoon, I visited the site and met with local officials. Jill and I are keeping those injured in our prayers, and we’re grateful for the first responders. They deserve an incredible amount of credit.”

3:20 p.m.

President Joe Biden speaks at Mill 19 in Hazelwood. (Alexandra Wimley/Post-Gazette)

Mr. Biden delivers his infrastructure address at Mill 19 in Hazelwood.

He touts his $1 trillion spending package on the country’s infrastructure, with $1.6 billion of it going to Pennsylvania.

“We can’t slow down now“ Mr. Biden says. ”We know what happens when we stop investing in the future in a place like Pittsburgh.”

4:30 p.m. Rescue crews finish searching beneath the bridge for any other casualties.

“We did what we did. I think we did it very, very well. I think the outcome was very, very good,” Chief Jones says. “Was it all based on our skills and training? No. You have to have a little bit of luck in there. But luck favors the prepared, and we were prepared in this situation.”

6 p.m. Chief Jones said emergency crews were transitioning from the response phase to the recovery phase, preparing in coming days to remove the private vehicles and the Port Authority bus from the ravine.

Bill Godshall of Greenfield takes a look at a bridge collapse above Fern Hollow Creek along Forbes Ave. “I hike these bills all the time, I drive that bridge everyday,” said Godshall, mirroring the statements of many others who came to get a closer look at the site. (Stephanie Strasburg/Post-Gazette)