Investigators have discovered he kept a list that appeared to have targets of violence, John Bennett, the Federal Bureau of Investigation agent in charge in the San Francisco office, told the news conference.
The suspect, Santino William Legan, 19, meant to target other churches, religious groups political parties and other organizations that are nationwide, Federal Bureau of Investigation (FBI) official said on Tuesday, declining to identify additional suspected targets.
In their ongoing quest to understand Legan's motives, FBI investigators revealed Tuesday that they have found material suggesting that Legan was collecting violent ideologies, and he himself had "a fractured ideology", with apparent animus toward both ends of the political spectrum, the government in general, and multiple religions.
Officials on Tuesday revealed they had discovered gunman Santino William Legan's "target list" which included religious and federal buildings.
"We have uncovered evidence throughout the course of our investigation that the shooter was exploring violent ideologies", Bennett said.
They are also trying to determine whether anyone else knew about the attack beforehand, Bennett said, and "why he committed this specific act of violence".
Bennett said investigators have not come across any statement on the incident by the shooter, but they did find indications of violent beliefs.
"Due to the discovery of the target list, as well as other information we have encountered in this investigation, the FBI has opened a full domestic terrorism investigation into this mass shooting". Twelve others were wounded at the popular Gilroy Garlic Festival some 80 miles southeast of San Francisco. On Thursday, the agent had noted that written materials taken from Legan's residence in Nevada ran the ideological gamut.
"To the families of Stephen Romero, Keyla Salazar, Trevor Irby, and to the injured that survived this tragedy, we can not begin to describe our despair at his actions", the statement continues.
As the officers were shooting at Legan, hitting him "multiple times" with rounds from their handguns, the suspect fell to the ground and fatally shot himself in the head, Gilroy Police Chief Scot Smithee said last week. He had a 75-round drum magazine that fit into his weapon, and there were 71 rounds left in the drum when he died. "We want to express our deepest and sincerest apologies for the loss and pain that he has caused", the statement read.
"This is a domestic terrorism case", U.S. Attorney John Bash said Sunday of the El Paso shooting.
In order to initiate a federal terrorism investigation, authorities must have reason to believe that a suspect's act of violence was "motivated by their ideology", Bennett said.
Authorities said they found more ammunition, a rifle scope, flashlight and shovel in a bag in a nearby creek.
"The suspect was hit by the police officers' gunfire multiple times", he said. However, the organizations on the list were "nationwide", not specifically Santa Clara County, he added.