On Tuesday afternoon Nasim Aghdam opened fire at YouTube’s headquarters in San Bruno, California.
She shot three people – though none fatally – and was found dead of a self-inflicted gunshot wound to the chest.
Here, moment by moment, is how the event unfolded.
This post will be updated as more information emerges.
April 2, 2018: Nasim Aghdam is reported missing from her hometown of San Diego, California. Her father is worried she may be heading for YouTube HQ, and tells police.
April 3, 1:40 am.: Police in Mountain View, California, find Aghdam asleep in her car in a parking lot. They speak for 20 minutes.
2:00 am.: Officers leave Aghdam. They said she was "calm and cooperative" and told them she had no plans to hurt anybody. They let her family know where she is.
Business Insider has also published a fuller account of the parking lot exchange.
3:00 am.: Aghdam's father returns a call from Mountain View police. He explained her apparent anger at YouTube, but "did not seem concerned" that anything bad may happen.
Later that morning: Aghdam drives from Mountain View to San Bruno. The precise time is unclear.
San Bruno police say Aghdam visited a "local" gun range before the attack, but did not say which one. Pictured below are search results for shooting ranges in the area.
After finishing at the range, Aghdam parked near YouTube HQ and entered the campus on foot via a parking garage.
12:46 p.m.: San Bruno police receive the first 911 calls from people at YouTube HQ reporting gunshots.
12:48 p.m.: Police arrive and start searching the building.
12:57 p.m.: Word starts to get out. YouTube employee Vadim Lavrusik tweets that he is hiding from the shooter behind a makeshift barricade.
Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers.
— Vadim Lavrusik (@Lavrusik) April 3, 2018
1:01 p.m.: San Bruno police post a tweet warning of "activity" around YouTube HQ, but do not yet describe it as a shooting.
Police activity at 901 Cherry Ave, please stay out of the area. pic.twitter.com/H6iAj0g7ra
— San Bruno Police (@SanBrunoPolice) April 3, 2018
1:05 p.m.: Business Insider first reports the shooting.
1:10 p.m.: YouTube product manager Todd Sherman tweets that other employees told him the shooter had already shot herself.
https://twitter.com/tdd/status/981262647097147392?ref_src=twsrc%5Etfw
Sherman also describes seeing bloodstains on the floor and stairs of the building as he fled.
https://twitter.com/tdd/status/981262648867143680?ref_src=twsrc%5Etfw
1:13 p.m.: 16 minutes after his first tweet, Lavrusik says he is outside and safe.
Safe. Got evacuated it. Outside now.
— Vadim Lavrusik (@Lavrusik) April 3, 2018
1:28 p.m.: San Bruno police tweet again, this time acknowledging an "active shooter" situation.
We are responding to an active shooter. Please stay away from Cherry Ave & Bay Hill Drive.
— San Bruno Police (@SanBrunoPolice) April 3, 2018
1:30 p.m.: Google acknowledges the shooting.
Re: YouTube situation, we are coordinating with authorities and will provide official information here from Google and YouTube as it becomes available.
— News from Google (@NewsFromGoogle) April 3, 2018
Around 2.18 p.m.: Lavrusik's account is hacked and used to spread misinformation about the shooting.
Someone appears to have hacked the account of @Lavrusik, a @YouTube employee, which seems like an incredibly indecent thing to do after a shooting. pic.twitter.com/s6GDpRxjxf
— Ken Schwencke (@schwanksta) April 3, 2018
Messages from Lavrusik's account, which had previously posted true information about the shooting, wrongly named Daniel "Keemstar" Keem as a potential victim. In reality, he was not involved at all.
Business Insider's Rob Price has written in more detail on hoaxes published around this shooting.
2:25 p.m.: Local TV news reports that the shooter is dead.
#Breaking: Female suspect dead. Shooting at #YouTube headquarters in San Bruno (near #SFO). Livestream @nbcbayarea
— Raj Mathai (@rajmathai) April 3, 2018
2:37 p.m.: Injuries are confirmed. Police initially say four people have gunshot wounds, this is eventually revised down to three.
San Bruno Police confirm four victims have been taken to hospital for gunshot-related injuries following the @YouTube headquarters shooting. Another person is dead from a suspected self-inflicted gunshot.
MORE: https://t.co/8jUITV2ii2 #FirstEdition pic.twitter.com/FYWpiUZrKO
— Sky News Australia (@SkyNewsAust) April 3, 2018
2.49 p.m.: President Donald Trump sends his "thoughts and prayers" to those affected.
Was just briefed on the shooting at YouTube’s HQ in San Bruno, California. Our thoughts and prayers are with everybody involved. Thank you to our phenomenal Law Enforcement Officers and First Responders that are currently on the scene.
— Donald J. Trump (@realDonaldTrump) April 3, 2018
3:14 p.m.: Surgeons at Zuckerberg San Francisco General Hospital say the three victims are being treated, and range from "critical" to "fair".
4:34 p.m.: Google CEO Sundar Pichai sent a letter to all Google employees describing the "unimaginable tragedy."
Here is the note that @sundarpichai just sent to Googlers worldwide. pic.twitter.com/bdC6KeTl9c
— News from Google (@NewsFromGoogle) April 3, 2018
6:19 p.m.: YouTube CEO Susan Wojcicki says the company "will come together and heal as a family."
There are no words to describe how horrible it was to have an active shooter @YouTube today. Our deepest gratitude to law enforcement & first responders for their rapid response. Our hearts go out to all those injured & impacted today. We will come together to heal as a family.
— Susan Wojcicki (@SusanWojcicki) April 4, 2018
6:58 p.m.: Media begin to name Nasim Aghdam as the shooter, citing law enforcement sources.
Breaking: Nasim Aghdam identified as the YouTube shooter. She had her own YouTube channel and apparently ranted against the company in her videos. Sources say she drove up to San Bruno from Riverside County, shot a man and 2 women before killing herself. #youtubeshooter
— Vicky Nguyen (@VickyNguyenTV) April 4, 2018
10:26 p.m.: San Bruno police name Nasim Aghdam as the shooter and publish a photograph.
The suspected shooter in today’s YouTube incident has been identified. Please see press release for details - https://t.co/Xvr2l9bB9s pic.twitter.com/NEBoX3WWK5
— San Bruno Police (@SanBrunoPolice) April 4, 2018
April 4, 2018, 4:07 p.m.: YouTube releases a statement clarifying that Nasim Aghdam accessed the premises through a parking garage, and reached an outdoor courtyard where the violence unfolded. She never made it inside the building, the statement said.
An update from YouTube. pic.twitter.com/HG4LgCupRi
— News from Google (@NewsFromGoogle) April 4, 2018
YouTube says it will increase security at all of its offices worldwide as a result of the incident.
"We are also revisiting this incident in detail and will be increasing the security we have at all of our offices worldwide to make them more secure not only for the near term, but long term," the statement read in part.
"We want to express our deepest gratitude to the first responders, including the police, fire department, and medical teams. And a huge thank you also to the wider global community for their outpouring of support, well wishes, and words of togetherness."
YouTube's statement continued: "Your support reminds us that even in the toughest of times, the YouTube community comes together and supports one another."