Someone sprinted through the doors with a dire warning: "There is a man with a knife up there, and he's coming this way."

"Everyone ran to the back of the restaurant and crouched down, trying to hide themselves from view," witness Elsbeth Smedley told CNN.

Smedley was among the crowd taking shelter inside Elliot's, a café just a few blocks south of London Bridge.

A man with a "massive knife" charged into the restaurant, Smedley said. And some people weren't able to escape.

His target: a waitress hiding behind a partition.

"He stabbed her in the neck," Smedley said. "He stabbed another man in the back, and then he ran out of the restaurant."

Some inside the restaurant thought there might have been another man armed with a knife, too, Smedley said, but it was too chaotic to see clearly.

The stabbing rampage was part of a terror attack Saturday night . A few blocks away, a van mowed down pedestrians on London Bridge.

Seven people were killed and 48 others wounded, police said. The three attackers were shot dead.

As authorities work to piece together what happened, witness accounts paint a harrowing picture of the panic that spread across the popular Borough Market pub and restaurant neighborhood.

'Everyone kept down'

Simon Thompson said he saw chaos near the main entrance to the market.

"People started running and shouting," he said. "It's a bit of a blur, but I saw people on the floor. A taxi driver began screaming for people to run, and everyone did."

Video from inside a nearby bar shows people flattening themselves on the ground as police shout at them to take cover -- fast.

JUST WATCHED Bar patrons scramble, take cover Replay More Videos ... MUST WATCH Bar patrons scramble, take cover 00:48

"They told us to remain on the floor, but to stay calm," said Paul Connell, who was having drinks with friends at Katzenjammers bar when officers rushed in.

Down the street, the owner of Applebee's Fish Market scrambled to pull down metal shutters at the front to protect people inside his restaurant.

"About five minutes later, there were gunshots everywhere," Jack Applebee told CNN.

Outside, Applebee said, one of his colleagues had spotted men wearing what he feared were suicide vests.

For 90 minutes, everyone huddled upstairs. Gunshots erupted six or seven times, he said.

"Everyone kept down. Just sort of -- just trying to keep everyone okay," he said. "It was just crazy."

A witness photo taken on the street near his restaurant showed what appeared to be two suspects on the ground.

Photos: London Bridge, nearby cafe target of terror attack Forensic officers work at the scene of a terror attack at London Bridge in London on Sunday, June 4. At least seven people were killed in attacks late Saturday as a van mowed down pedestrians on London Bridge before attackers then stabbed victims at nearby Borough Market. Hide Caption 1 of 26 Photos: London Bridge, nearby cafe target of terror attack Counterterrorism officers patrol near the scene of the attack on London Bridge. When speaking to the media on Sunday, British Prime Minister Theresa May did not announce any increase in the UK terror threat level. Hide Caption 2 of 26 Photos: London Bridge, nearby cafe target of terror attack A woman reacts after asking a Police officer to lay flowers near London Bridge as a tribute to the victims of the attack. Hide Caption 3 of 26 Photos: London Bridge, nearby cafe target of terror attack UK police officers on Sunday continue their investigation into the terror attacks on London Bridge and in a nearby restaurant district. The attacks on June 3 came days before a general election and two weeks after 22 people were killed when a suicide bomber targeted an Ariana Grande concert in Manchester. Hide Caption 4 of 26 Photos: London Bridge, nearby cafe target of terror attack Prime Minister Theresa May makes a statement at 10 Downing Street, following a Cobra security meeting in response to Saturday night's terror attack. Violence must "never be allowed to disrupt the democratic process," May said, adding that Thursday's general election will go ahead. Hide Caption 5 of 26 Photos: London Bridge, nearby cafe target of terror attack Abandoned buses line London Bridge as the scene remains under investigation following the attack. Metropolitan Police Assistant Commissioner Mark Rowley said in a statement Sunday that a white van struck pedestrians on London Bridge. Attackers then left the vehicle and "a number of people were stabbed, including an on-duty British Transport Police officer who was responding to the incident at London Bridge," said Rowley. The officer received serious but not life-threatening injuries. Hide Caption 6 of 26 Photos: London Bridge, nearby cafe target of terror attack Counter terrorism officers move up an escalator under The Shard, an iconic highrise near the scene of last night's London Bridge attack. Hide Caption 7 of 26 Photos: London Bridge, nearby cafe target of terror attack A group of police forensic officers walks in the street outside Borough Market. Hide Caption 8 of 26 Photos: London Bridge, nearby cafe target of terror attack People lie on the ground after being detained by police at Elizabeth Fry apartments in Barking, east London, which officers raided Sunday, June 4, following Saturday's terror attack at London Bridge and Borough Market. Hide Caption 9 of 26 Photos: London Bridge, nearby cafe target of terror attack A bouquet of flowers left near the police cordon at London Bridge on June 4. Hide Caption 10 of 26 Photos: London Bridge, nearby cafe target of terror attack A view from above shows where a van struck pedestrians on London Bridge -- and then crashed into a barrier. Hide Caption 11 of 26 Photos: London Bridge, nearby cafe target of terror attack This image, from London's Borough Market, shows two of the attackers after they were shot by London police. The attackers drove a white van into pedestrians on London Bridge, leaving bodies lying in the roadway, a witness to the incident told CNN Hide Caption 12 of 26 Photos: London Bridge, nearby cafe target of terror attack Armed police patrol near London Bridge on Saturday, June 3. Mayor Sadiq Khan said it was a "deliberate and cowardly attack" on Londoners enjoying Saturday night out. Hide Caption 13 of 26 Photos: London Bridge, nearby cafe target of terror attack The white van used in the attack is seen near London Bridge. Hide Caption 14 of 26 Photos: London Bridge, nearby cafe target of terror attack Police carry out a search near empty buses on London Bridge, Saturday, June 3. Hide Caption 15 of 26 Photos: London Bridge, nearby cafe target of terror attack A person is treated for injuries near London Bridge. Hide Caption 16 of 26 Photos: London Bridge, nearby cafe target of terror attack Members of the public flee after reports of the incident involving a vehicle and pedestrians. Hide Caption 17 of 26 Photos: London Bridge, nearby cafe target of terror attack Police and emergency responders attend to an injured person. Hide Caption 18 of 26 Photos: London Bridge, nearby cafe target of terror attack An armed Police officer gestures after the attack in central London. Hide Caption 19 of 26 Photos: London Bridge, nearby cafe target of terror attack Guests from the Premier Inn Bankside Hotel are evacuated following the attacks. Hide Caption 20 of 26 Photos: London Bridge, nearby cafe target of terror attack A woman wearing an emergency blanket talks on her phone at London Bridge train station. London Bridge Tube station was closed and London Bridge was closed in both directions. Hide Caption 21 of 26 Photos: London Bridge, nearby cafe target of terror attack Armed police raid The Blue Eyed Maid on Borough High Street. Hide Caption 22 of 26 Photos: London Bridge, nearby cafe target of terror attack Debris and abandoned cars remain at the scene of one of the incidents. Hide Caption 23 of 26 Photos: London Bridge, nearby cafe target of terror attack Police sniffer dogs are seen at London Bridge. Hide Caption 24 of 26 Photos: London Bridge, nearby cafe target of terror attack A helicopter flies near London Bridge. Hide Caption 25 of 26 Photos: London Bridge, nearby cafe target of terror attack People are led to safety on Southwark Bridge, away from London Bridge. Hide Caption 26 of 26

'The van was aiming at the people'

One thought ran through Mark Roberts' mind as he watched a car plow into pedestrians on London Bridge Saturday night.

"Which direction should I run?"

Roberts froze as he saw a van swerve into oncoming lanes and strike a crowd of people at the iconic site. One person, he said, flew 20 feet in the air.

"It looked to me that the van was aiming at the people," he said.

JUST WATCHED Witness: Van hit pedestrians on bridge Replay More Videos ... MUST WATCH Witness: Van hit pedestrians on bridge 02:47

Police and emergency vehicles rushed to the scene.

Hundreds of people are evacuated from #LondonBridge after unconfirmed accident brings more than 15 police cars and helicopters come to scene pic.twitter.com/IfQLMOXsR0 — Kaine Pieri (@PieriKaine) June 3, 2017

"I heard a boom behind me," said Brad Myers, who was underneath the bridge snapping photos.

JUST WATCHED Witness: Someone jumped off bridge into water Replay More Videos ... MUST WATCH Witness: Someone jumped off bridge into water 01:12

Myers said he saw a white vehicle slam into the guard rail, then plow into a group of pedestrians he'd been standing alongside only a few minutes earlier.

As the horrifying scene unfolded, Myers said he saw one person's desperate attempt to escape the attack.

Someone jumped off the bridge, he said, and into the water below.