How the San Bernardino Shooting Unfolded

— -- Mass casualties and fleeing suspects created chaos in San Bernardino, California, Wednesday.

A late-morning rampage led to 14 deaths and 21 injuries, making it the deadliest mass shooting in the United States since the 2012 Newtown, Connecticut, attack.

Here is a timeline of how the events unfolded.

11:00 a.m.

The first calls to 911 came at 11 a.m. from people inside the Inland Regional Center.

"It was quickly apparent we had what amounted to an active-shooter situation," San Bernardino Police Chief Jarrod Burguan said.

11:04 a.m.

It took police four minutes to arrive on the scene.

Multiple law enforcement agencies responded and police originally believed there were three suspects.

"They immediately entered the building in search of the suspects,” Burguan said. “Initial information is that the suspects were potentially still inside of the building."

About 11:20 a.m.

It took about 15 minutes for police to start extracting victims, get them to the triage center and then start transporting them to the hospital.

Police believed the alleged suspects fled the scene "potentially in a dark colored SUV."

2:00 p.m.

While they were able to quickly remove the victims, clearing and securing the building took significantly longer.

"It is a massive facility, employs several hundred people. And it's taken a long time to clear the building," Burguan said.

At a 2 p.m. news conference, Burguan said he thought "we still have assets inside that are completing that clearing process."

2:30 p.m.

The injured patients were sent to two hospitals, one of which received what was believed to be a credible bomb threat.

Loma Linda University Medical Center received the most serious patients because it is the only level-one trauma center in the region, and it was told by law enforcement there was a genuine threat.

"Hospital protocols were initiated as requested by law enforcement," hospital spokeswoman Briana Pastorino. "Because of that bomb threat, Loma Linda University classes were canceled and students were encouraged to leave the public areas of campus. We worked with law enforcement to proactively."

That bomb threat was lifted at 3:30 when "law enforcement said the threat was indeed not credible and that our campus was safe," Pastorino said.

Around 3:15 p.m.

Police have not released specific timing for the rest of the events, but they fielded tips mid-afternoon that led them to the city of Redlands, directly to the east of the attack site.

Police cars were seen speeding toward Redlands, leading to a shootout.

"When officers set up on the residence to watch it, there was a vehicle seen leaving that was suspected of possibly being involved," Burguan said at a 5 p.m. police news conference. "There ended up being a pursuit of the vehicle and that pursuit came back to San Bernardino Avenue between Mountain View and Richardson here in the city of San Bernardino, where the suspects’ vehicle stopped and there was an officer-involved shooting."

Police confirmed that there was an exchange of gunfire, and both suspects -- one male and one female -- were killed in the shootout with police, while one officer suffered non-life-threatening injuries.

Helicopter footage of a bullet-riddled SUV was made by news helicopters and one of the suspects appeared to be lying in the street while another body was seen later being removed from the vehicle.

"They were dressed in kind of assault-style clothing. ... They were both armed with assault rifles," Burguan said of the suspects.

The investigation continued through the rest of the afternoon and evening, as police initially worked to ensure that there was not still a third suspect on the loose.

"We initially put out that there was information that there was upwards of three shooters,” Chief Burguan said. “It really looks like we have two shooters that we believe went into the building are the two shooters that are deceased.”

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