Tech: A tragic day at YouTube: Photos show the chaotic scene as police responded to the shooting (GOOG, GOOGL)

With at least three injured and one dead at the YouTube San Bruno office, many details have yet to be revealed.

On Tuesday, a shooter opened fire at the YouTube headquarters in San Bruno, California.

YouTube employees were eating lunch in an open-air courtyard at the time the shooter, who has been identified by police as a woman, entered. Three people were injured by gunfire.

Police arrived within five minutes of the shooting, according to local law enforcement, and found the shooter dead inside the building from a self-inflicted gunshot wound.

Business Insider reporters were on the scene in the aftermath of the incident, as YouTube employees and bystanders waited for police to sweep the area and ensure they were safe.

Here are the first photos from YouTube headquarters in the hours after the shooting.

When we arrived around 1 p.m., YouTube employees and bystanders, some visibly shaken, were standing in a nearby parking lot after being evacuated from the office buildings.

Around 2 p.m., police told YouTube employees and Business Insider reporters that there was an active shooter situation and that no one was allowed to leave the parking lot.

"There is a suspect outstanding. You guys are in a safe space," a police officer said.

Police asked YouTube employees if they had witnessed the shooting. About 15 people in a crowd of hundreds raised their hands and joined officers to the side of the parking lot.

YouTube CEO Susan Wojcicki was seen walking away from the office buildings as law enforcement continued to investigate the scene. "Pls stay secure as police clear building and pls follow police instructions to safety," Wojcicki said in a note to staff.

"We have full team here to get you to safety," she added.

The memo was first reported by Recode.

An official at San Francisco General Hospital confirmed in a press meeting at 3:30 p.m. that the hospital was treating three people — two women and one man — for gunshot wounds.

Police officers covered the YouTube campus and blocked off the office buildings with tape.

The FBI was called in, as well.

YouTube employees were overheard saying they left their personal belongings inside.

There's a shopping plaza, anchored by a Carl's Jr. restaurant, located across Cherry Avenue from the YouTube campus. Witnesses ran down the street in the moments after the shooting.

A woman with a gunshot wound in the leg sought refuge at Carl's Jr. restaurant. Employees and customers came to her aid and tried to staunch the bleeding until an ambulance arrived.

A spokesperson for the Carl's Jr. parent company confirmed the event to Business Insider.

Dennis, the owner of Hashes & Brews, was having a cigarette break outside when he heard loud banging noises that he thought was a nail gun from someone doing construction.

Suddenly he saw "a whole bunch of people just trampling over each other, coming out the front doors of YouTube. They were running, people just running," he told Business Insider.

Dennis, who declined to give his last name, said he waved a group of three of them into the restaurant. One man was bleeding from the face, but the wound did not appear severe.

A woman had a bullet lodged in the sole of her leather shoe. "They were shaking, they were making me shake. This is a situation where you see in the movies, not in real life," Dennis said.

After law enforcement declared the scene was safe again, charter buses arrived to bring YouTube employees away from the campus. But employees weren't allowed back inside.

Hours later, a small press conference was held on a law outside the office buildings. Chris Dale, global head of communications and public affairs for YouTube, addressed reporters.

"We are an incredibly tight knit community within YouTube, where it feels like a family," Dale said. "Today, it feels like the entire community of YouTube and all of the employees were victims of this crime."