A 32-year-old woman was brought to the hospital in serious condition and a 27-year-old woman was taken there in fair condition on Tuesday.
Manny Mendoza, the store's rangemaster, confirmed the purchase Thursday afternoon but said the transaction was not memorable. Witnesses previously told KTVU that one of the victim's was Aghdam's boyfriend.
Three people were wounded in the shooting and a fourth injured their ankle in the chaos before Aghdam turned the handgun on herself.
Investigators declined to say why they were there.
He said the 9mm Smith & Wesson handgun was legally purchased January 16 and registered in her name.
Nasim Aghdam had a large internet presence, before her clips and account was deleted in the aftermath of the shooting. He also thanked law enforcement and responders who are on the scene. "Youtube filtered my channels to keep them from getting views!"
Investigators will likely scrutinize Aghdam's movements during the almost nine-hour drive from her family's home near San Diego to the YouTube campus, examine the freakish videos she posted online and look for any messages she may have sent to company officials.
Aghdam had frequently posted her own videos under a pseudonym on the platform - featuring a vast array of eclectic content, from exercise instruction to pop music parodies, spoken in English, Farsi and Turkish - and she said YouTube had begun "filtering" those videos to reduce the number of views and her advertising revenue.
Her father told the Bay Area News Group that his daughter was angry at YouTube because it had "demonetised" her videos - meaning she was not earning money.
Hours before officers were called to YouTube's headquarters after being informed of an armed intruder, they had spotted the assailant parked in her auto and sleeping in a Walmart parking lot.
Police are investigating a website that appears to show the same woman lambasting YouTube for restricting her videos.
The license plate on a vehicle towed from YouTube's campus Tuesday is reportedly registered to Aghdam.
She explained she'd left home due to family problems and remained calm throughout the conversation, Mountain View Police Chief Max Bosel said.
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"At no point did her father or brother mention anything about potential acts of violence", the police statement continued. They did not know she had a gun.
In an Instagram post from March 18 she said the video sharing website was using its tools to "censor and suppress people who speak the truth and are not good for the financial, political gains of the system and big businesses".
"It was a woman and she was firing her gun".
She then fatally shot herself.
She and others hid in a conference room for an hour while another employee repeatedly called 911 for updates.
Aghdam was prolific at producing videos and posting them online. The headquarters has more than a thousand engineers and other employees in several buildings.
The gunfire started shortly before 1 p.m.at the company's headquarters about 10 miles from San Francisco.
Inside, Google several years ago famously outfitted the office with a 3-lane red slide for workers to zoom from one story to another. Rather, law enforcement said, "She was upset with YouTube".
In a separate tweet, Mr Pichai said he and YouTube Chief Executive Susan Wojcicki were "focused on supporting our employees and the @YouTube community through this hard time together".
He got on his skateboard and approached a courtyard, where he saw the shooter yelling, "Come get me".
He saw somebody lying nearby on his back with a red stain on his stomach that appeared to be from a bullet wound. He jumped on his skateboard and took off.
"This will be a long and very methodical investigation", said Geoff Caldwell, a police commander in San Bruno, a city just south of San Francisco where YouTube is located.