Authorities are investigating the deadly Gilroy Garlic Festival shooting as domestic terrorism after discovering the gunman had a "target list" — including churches, courthouses and locations specific to both political parties.

Santino William Legan, 19, is accused of firing 39 rounds with an AK-47-style rifle at the California food festival on July 28, killing three people and injuring 13 others, according to officials. He was hit multiple times by police before turning his weapon on himself.

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The FBI has opened a domestic terrorism investigation into the case, according to John Bennett, the FBI's agent in charge in San Francisco. He told reporters Tuesday a motive is still unclear in the shooting, and noted the suspect appeared to have conflicting ideologies.

He revealed investigators discovered a "target list" compiled by the gunman, that included nationwide religious institutions, federal buildings, courthouses and locations identified with both major political parties — but didn't include the names of people. He said the Gilroy Garlic Festival was among the targets.

The gunman was wearing a bulletproof vest and had multiple magazines on his body and on the ground as he opened fire. Authorities added they found additional magazines, a rifle scope, flashlight and shovel in a bag in a nearby creek.

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Keyla Salazar, 13, Trevor Irby, 25, and Stephen Romero, 6, died in the shooting.

The following weekend, another 31 people were killed in mass shootings in Dayton, Ohio, and El Paso, Texas.