By Alex Dobuzinskis

(Reuters) – The FBI has opened a domestic terrorism investigation into a California mass shooting by a 19-year-old gunman who killed three people at a food festival last week, officials said on Tuesday.

Authorities have said they still do not know what motivated Santino William Legan, 19, to fire an assault-style rifle into a crowd in Gilroy, California, on July 28. His victims included a 6-year-old boy and a 13-year-old girl.

Police officers exchanged gunfire with Legan, who was wearing a bullet-resistant vest, and struck him, Gilroy Police Chief Scot Smithee said at a news conference on Tuesday. Legan killed himself with a gunshot to the head.

Investigators have discovered he kept a list that appeared to have targets of violence, John Bennett, the FBI agent in charge in the San Francisco office, told the news conference.

One of those potential targets was the one he attacked, the annual Gilroy Garlic Festival, Bennett said. The decades-old event celebrates produce from California’s countryside and is held about 70 miles (110 km) south of San Francisco.

“The shooter appeared to have an interest in varying, competing violent ideologies,” Bennett told reporters.

“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.”

RACIST TREATISE

Before the shooting, Legan had posted on his Instagram page a photograph showing a sign warning of a high danger of forest fires. Its caption urged people to read “Might is Right,” a racist and sexist treatise written in the 19th century.

FBI investigators are considering Legan’s Instagram posts as they seek to determine his motivation and are exploring whether he was motivated by white nationalism, Bennett said.

Legan’s target list, which he kept on at least one digital device, had organizations from across the country and included religious institutions and political organizations affiliated with both the Democratic and Republican parties, Bennett said.

Legan left no manifesto, Bennett said, declining to provide other details on his ideological leanings.

Legan fired 39 rounds and the three officers who confronted him fired 18, Smithee said, and Legan had more than 200 rounds of ammunition on or near his body.

Legan’s family in a statement on Tuesday apologized to the families of the three people he killed and to the wounded, according to the Los Angeles Times.

“We have never and would never condone the hateful thoughts and ideologies that led to this event, and it is impossible to reconcile this with the son we thought we knew,” the statement said.

Members of Legan’s family could not immediately be reached for comment.

(Reporting by Alex Dobuzinskis in Los Angeles; editing by Bill Tarrant and Jonathan Oatis)