Immigration officials say a gunman who killed his three daughters and a chaperone in a Northern California church this week was in the United States illegally.

A U.S. Immigration and Customs Enforcement spokeswoman told The Associated Press on Friday that David Mora overstayed his visa after entering California from Mexico in December 2018. Mora killed himself after the shooting.

The Merced County Sheriff’s Office said because of California's so-called sanctuary state law it did not inform immigration officials last week that Mora had been arrested for punching an officer.

The development provides a possible motive because Mora could have been deported, separating him from his daughters. Investigators aren't commenting.