A law enforcement source with knowledge of the investigation told federal authorities that "anti-Islamic writings" were recovered in a vehicle connected to the two teenagers suspected in Monday's attack at the Islamic Center of San Diego, which resulted in three fatalities.
The alleged shooters have been identified by officials as Caleb Vasquez, 18, and Cain Clark, 17. Police located the two teenagers dead inside their car after the incident; investigators said the deaths appeared to be self-inflicted gunshot wounds.
Local reporting has previously published the suspects' names and reported on the contents of the writings. Federal and local investigators have said the attack is being examined as a hate crime, though authorities declined to provide additional detail about a possible motive during early stages of the inquiry.
Authorities said that Clark's mother is cooperating with investigators. Police response to the unfolding situation began after a call from the mother of one of the teenagers, who described her son as suicidal and reported he had left with three of her firearms and her vehicle, according to law enforcement accounts.
Initial police activity took officers to a nearby shopping mall and to the boy's school before dispatchers received calls reporting the shooting at the mosque. The Islamic Center of San Diego, described by officials as the largest mosque in San Diego County, also houses the Bright Horizon Academy. Authorities confirmed that all students at the academy were safe and accounted for following the attack.
The victim community has mobilized fundraising in the immediate aftermath. A campaign organized by CAIR San Diego together with the Islamic Center of San Diego has raised more than $1.7 million for the family of the slain security guard, Amin Abdullah. Authorities have credited Abdullah with actions that prevented further bloodshed during the attack.
City officials said they would increase security across San Diego. Mayor Todd Gloria, speaking to national media, expressed concern about the potential for the incident to inspire copycat attacks. He said, "There’s always a concern about other sick and twisted individuals who will take inspiration from this tragedy and try and replicate," and pledged that "No expense will be spared in protecting the people of this city."
The investigation remains active and limited public details have been released as authorities continue to gather evidence and interview witnesses. Officials have declined to elaborate on the motive beyond confirming the hate crime designation, and the content of the materials found in the vehicle has only been described generally by investigators and earlier local reports.