GILROY, Calif. (AP) The 19-year-old gunman who opened fire at a Northern California food festival was kind of a loner and much of his life was shrouded in mystery, the FBI said Tuesday as investigators searched for a motive.

Police believe Santino William Legan fired randomly Sunday, killing three people, after cutting through a fence to get into the Gilroy Garlic Festival. Officers patrolling the popular event responded within a minute and killed him.

Legan attended high school in Gilroy in his senior year and was recently living in Nevada, where he purchased two guns the AK-47-style semi-automatic rifle he used in the attack and a shotgun that was found in his car near the festival, authorities said.

A bag of ammunition was found in a creek near the fence, police said.

We understand him to be kind of a loner, said Craig Fair, deputy special agent in charge of the FBIs San Francisco Division. People who act alone are exceptionally dangerous because they ... may not communicate their plans, intentions, mindset they may not impart that on other people.