The two teenage suspects who opened fire on a San Diego mosque scrawled hate rhetoric on their weapons before carrying out the attack, police said.
Investigators said they are also probing anti-Islamic writings that were also found inside a vehicle believed to be linked to the gunmen.
After fatally killing three victims outside the place of worship on Monday, both shooters died from self-inflicted gunshot wounds.
They were identified as Cain Clark, 17, and Caleb Vazquez, 18, according to NBC News.
Officials told CNN that hate speech was inscribed on one of the weapons used in the attack.
Authorities said in a Monday night news conference that police first received a call about a 'runaway juvenile'.
A mother of one of the teens reported that her son was suicidal, and several of her weapons were missing.
She had also found a note that her son left behind. 'That began to trigger a larger threat assessment picture,' Police Chief Scott Wahl said.
Police described both teens as being dressed in camo fatigues and referred to the car they used as a 2018 BMW X1 SUV, on their radios shortly after the incident.
One officer said on the radio that guns 'stolen from the house’ included 'a 9mm handgun, a shotgun and a mini 14’.
Cain Clark, 17, and Caleb Vazquez, 18, were found dead from self-inflicted gunshot wounds after the shooting on Monday
Security guard Amin Abdullah has been identified as one of the victims of the shooting on Monday
One of the victims was security guard Amin Abdullah, a father of eight children.
His friend Anees Faraj, a fellow security guard at the mosque who was not working, described the events as shocking and confirmed Amin as the guard who died.
Police Chief Wahl said that Amin and his actions helped prevent an even deadlier attack.
He added: 'His actions were heroic and he undoubtedly saved lives today.'
TV footage from a helicopter showed armed response teams gathered outside a building, with one unidentified person lying in a pool of blood.
The imam of the mosque confirmed that no children were injured during the shooting.
The place of worship is also home to the Al Rashid school, which educates children from kindergarten to the third grade.
Panicked parents arrived at the scene to retrieve their children after two teenage gunman opened fire
Imam Taha Hassane said: 'The entire school is safe. All the kids, all the staff and the teachers are safe out of the Islamic Center.
'We have a few casualties, not confirmed yet. There is no threat at this moment, but we want everyone to stay away from the Islamic Center of San Diego.'
Crowds of young students were seen being evacuated from the building by law enforcement officers.
Panicked parents rushed to the scene to pick up their children after police set up a reunification site at San Diego Clairemont Seventh-Day Adventist Church.
Many in the crowd were seen using their phones to discover what happened while one woman crouched down outside the place of worship as the terror unfolded.
The mosque is the largest in San Diego County, according to its website, and is located around nine miles north of the downtown area.
