Police are investigating the attack as a hate crime after officers found hate speech written on one of the weapons(Representational image)|CC BY-NC 4.0

A shooting at the Islamic Center of San Diego left three people dead on Monday, including a security guard praised by police for acting heroically and helping save lives. 

Authorities later found two teenage suspects dead inside a nearby car from suspected self-inflicted wounds. One of them was identified as 17-year-old Cain Clark.

Police are investigating the attack as a hate crime after officers found hate speech written on one of the weapons and a suicide note containing racial pride messages. 

Hours before the shooting, Clark’s mother had warned police that her son, her car, and three weapons were missing.

The mosque also houses a school, raising fears among families and worshippers. FBI agents and state prosecutors joined the investigation as officials examined whether the suspects had planned additional attacks.