BALTIMORE, United States–With a huge, runaway cargo ship bearing down on one of Baltimore harbor's busiest bridges, local police had just moments to react to a last-ditch Mayday call from its crew.

Stopping the drifting container ship Dali was impossible.

But officers could still try to prevent drivers from heading into what was about to become a death trap.

"Hold all traffic on the Key Bridge. There’s a ship approaching that's just lost their steering, so until they get that under control, we've got to stop all traffic," an officer can be heard saying in police radio excerpts published by Broadcastify.

As his colleagues shut down the highway, an officer can be heard referring to nighttime repair workers already on the Francis Scott Key bridge -- six of whom were declared missing by officials after the disaster.

"If there's a crew up there you might want to notify whoever the foreman is, see if we can get them off the bridge temporarily," the officer says.

But it was too late.

"The whole bridge just fell down. Start, start -- whoever -- everybody. The whole bridge just collapsed," comes the next panicked message as the Dali slams into the structure.

Another officer radios in: "I can't get to the other side, sir, the bridge is down."

CCTV images tell the story -- showing much of the 47-year-old span crumpling and tumbling into the water, leaving the cargo ship with its piled containers wedged beneath crumpled steel.

- Shocked residents -

The calamity at a landmark familiar to tens of thousands of motorists a day left residents shocked.

At a gas station convenience store in Baltimore, Patricia Sisk regularly encounters harried commuters and stressed-out parents in the early hours.

But on the morning after the bridge collapse, the 82-year-old instead found herself greeting a stream of police officers, emergency personnel and worried locals.

"It's scary," Sisk, sporting her uniform cap, told AFP as sirens rang out.

"I've seen all these police officers and they told me what happened.... I feel for the people."

Sisk said several customers "thought it was an explosion. It was just horrible. They were scared."

Terrorism has been ruled out by officials in the drama. But Sisk said she hadn't had the same "creepy feeling" since the September 11, 2001 attacks in which Islamist hijackers triggered the collapse of New York's Twin Towers, leaving nearly 3,000 people dead.

"You know, when the towers.... and then you wonder," she said.

- 'Panicking and crying' -

Sisk spent the morning talking about the accident with customers at her cash register. Many were regulars who couldn't get where they needed to go anymore.

Jennifer Woolf, 41, told the harrowing tale of her son's brush with catastrophe.

After a late-night quarrel with his girlfriend, the 20-year-old hit the road. He crossed the bridge once, and then turned back to reconcile with his partner.

"He went back over the bridge a second time and as soon as he got over, (after) three minutes exactly, the bridge collapsed," Woolf explained as she got her morning coffee.

"He came home panicking and crying, like shaking, and I started crying," added the entrepreneur.

"He's still awake. He hasn't gone to sleep either... watching the news. He keeps texting me nonstop," Woolf said, adding that she was praying "for all the families that are going through the tragedy of looking for their loved ones."

With his breakfast, soda and cookies in hand, Baltimore resident Paul Kratsas said he had long feared that an incident like Tuesday's bridge collapse could happen.

"Yesterday, actually, I was going to use it," the 59-year-old Kratsas said of the bridge. "When I go over it, sometimes I'm like, 'Man, I hope this thing don't fall.'"

"These ships go in and out all the time," added the man, who came to check out the scene with his wife. "And they usually bring them in with big tugboats."

"Yeah, never seen that happen before," Kratsas said.