Family members have identified the young man who was killed at the party as Desiderio Romero V, known as Desi to some and Pepper to others.
Deputies responded around 10:15 p.m. Saturday to the area near Hale Avenue, where they found hundreds of people fleeing the scene, according to the Santa Clara County Sheriff's Office.
The shooting occurred during an unsanctioned birthday celebration for San Jose streamer "NateDeBaiits." Video from a Twitch livestream captured the moments when gunfire erupted and partygoers ran in panic. Authorities are reviewing the footage as part of their investigation.
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"We got to the party, we got patted down, there was security. From there, the party was going good until two groups started fighting," said an anonymous party witness. "I looked, I saw someone on the floor bleeding. He had a bullet hole in his chest next to where his heart would be."
The anonymous witness went on to say, "There was people, ripping T-shirts, tying the ends like some sort of bandage. They were applying pressure on the hole so that way they could stop the bleeding, but it was too severe. There's no security cameras. It's too dark even if you were recording, it would be hard to identify someone."
In a video sent to ABC7 Eyewitness News by witnesses, partygoers were frantically trying to help Desi after he was shot, but he died at the scene.
"NateDeBaiits" had promoted the event on social media as a celebration in an empty field along Hale Avenue. In an Instagram story following the shooting, he said he did not want any of the events to happen and that everything was out of his control.
The streamer also shared condolences for the victim in an Instagram story:
"My deepest condolences to his family and everyone who loved him. This doesn't even feel real. He was my classmate and my friend, and I am truly heartbroken," he said.
He also said that due to death threats, he will be moving out of San Jose.
Santa Clara County Sheriff's Office spokesperson Brooks Jarosz described the shooting as senseless violence at a Sunday press conference.
"Our hearts go out to all of those who've been affected by this, especially the families of the victims," Jarosz said. "This is not something we want to see in our community, this level of violence. But rest assured, our deputies and our detectives are committed to leaving no stone unturned and making sure that we find whoever did this and bring them to justice."
Authorities have said the incident was isolated, though no arrests had been made as of Monday.
Investigators said videos posted on social media have been helpful to the case. The Sheriff's Office is asking anyone with additional video footage or information to come forward as detectives continue what officials described as a lengthy and complex investigation.
The search for the shooter remains ongoing.
A GoFundMe page has now raised more than $18,000 dollars for Desi's funeral expenses.