The deadly San Diego “Mosque Killer” attack is being investigated as a possible act of domestic terrorism after authorities revealed the two teenage suspects were allegedly “radicalized online” and carried Nazi symbols, racist slogans, and extremist writings during the mass shooting outside the Islamic Center of San Diego.

Law enforcement officials said the gunmen killed three people outside the mosque before fleeing in a white BMW, where they later died from apparent murder-suicide gunshots. Federal investigators are now examining disturbing livestream footage allegedly recorded by the suspects before and after the attack.

Officials described the suspects as deeply immersed in violent extremist ideology and said they “did not discriminate on who they hated.”

More information about hate crime investigations can be found through the Federal Bureau of Investigation and the Department of Homeland Security.

Mosque Killer Suspects Radicalized Online

Authorities identified the suspects as Caleb Vasquez, 18, and Cain Clark, 17.

During a Tuesday press conference, investigators said both teens had embraced extremist ideology online and possessed a large cache of weapons, including more than 30 firearms and a crossbow.

Investigators also recovered writings and symbols associated with white supremacist ideology. According to officials, the suspects wore Nazi imagery during the attack, including the “Black Sun” symbol, a design linked to Nazi Germany and SS commander Heinrich Himmler.

Authorities said racist phrases such as “Race War Now” were etched onto the suspects’ weapons, and investigators recovered a manifesto praising Adolf Hitler and several notorious mass killers.

The FBI is reportedly investigating whether additional individuals may have had contact with the suspects online before the shooting.

Mosque Killer Livestream Video Under Investigation

One of the most chilling aspects of the case is the livestream footage allegedly recorded by the suspects during and after the attack.

According to law enforcement sources, the video shows the gunmen opening fire outside the Islamic Center before fleeing in their vehicle. The footage later captures a disturbing exchange between the two suspects inside the BMW.

Authorities said Vasquez repeatedly grabbed the barrel of Clark’s rifle and placed it against his own forehead while sitting in the passenger seat. The video reportedly had no audio.

The livestream later shows Clark fatally shooting Vasquez before turning the weapon on himself as the vehicle sat parked in a residential area near the mosque.

Federal investigators are continuing to analyze the footage as part of the ongoing terrorism probe.

Additional information about combating violent extremism is available at National Counterterrorism Center.

Victims Remembered by Community

Three men were killed during the attack outside the Islamic Center, including mosque security guard Amin Abdullah.

Family members and community leaders gathered Tuesday to honor the victims and condemn the hateful violence.

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Abdullah’s daughter, Hawaa Abdullah, delivered an emotional tribute to her father during a press conference.

“To me, my dad was a role model. He was a best friend. He was the best, absolute best dad in the world,” she said. “He was my protector.”

Community members described Abdullah as a devoted father and respected member of the mosque community.

Organizations monitoring hate crimes and extremism, including the Southern Poverty Law Center and the Anti-Defamation League, have warned about the growing threat of online radicalization among young extremists.

Growing Concerns About Online Extremism

The San Diego attack has renewed concerns among law enforcement and anti-extremism experts about the influence of online propaganda and extremist communities targeting young people.

Officials said the suspects appeared to consume and share violent ideological material online before carrying out the massacre.

Authorities are continuing to investigate whether the shooting was coordinated or inspired by broader extremist networks.

The tragedy has also prompted renewed calls for increased monitoring of extremist online content and expanded efforts to combat hate-fueled violence in the United States.