The FBI is opening a domestic terrorism investigation into the shooting at a popular California food festival that left three people dead, including two children, a law enforcement official said Tuesday.

The agency said Tuesday it has discovered a “target list” compiled by the gunman in a California mass shooting that listed nationwide religious institutions, federal buildings, courthouses and both major political parties. The festival was also on the list. 

Santino William Legan, 19, fatally shot three people, and injured 13, with a Romanian-made AK-47-style rifle before turning the gun on himself at the popular Gilroy Garlic Festival on July 28.

John Bennett, the FBI’s agent in charge in San Francisco, says authorities still have not determined a motive, and Legan appeared to be interested in conflicting ideologies.

Police officers carry evidence bags from the family home of gunman Santino William Legan on July 29. (Noah Berger/The Associated Press)

A separate mass shooting that killed 22 people at a crowded El Paso, Texas, store over the weekend is also being handled as a domestic terrorism case.

Federal investigators have fewer tools and legal powers at their disposal in domestic terrorism cases than they do if they are up against someone tied to an international organization such as the Islamic State in Iraq and Syria (ISIS) or al-Qaeda.

Law enforcement officials conducting international terrorism investigations, for instance, can get a secret surveillance warrant to monitor the communications of a person they think may be an agent of a foreign power or terror group.

Similarly, the U.S. Criminal Code makes it a crime for anyone to lend material support to designated foreign terror organizations, including ISIS and al-Qaeda, even if the investigation doesn’t involve accusations of violence.

There’s no domestic counterpart to that material support statute, meaning federal prosecutors must rely on hate-crime laws, weapons charges and other approaches that may not carry the terrorism label. Mere membership in, or support for, a white supremacist organization is not illegal.