Three worshippers and two teenage suspects were killed on Monday in a shooting at the Islamic Center of San Diego that authorities are investigating as a possible hate-motivated attack, according to police and local media reports.

The violence erupted shortly before noon at the mosque in San Diego's Clairemont neighborhood, prompting a large-scale law enforcement response and alarming Muslim communities across California.

San Diego Police Chief Scott Wahl said officers arrived within four minutes after receiving reports of an active shooter at the Islamic center. Police found three adults fatally shot outside the mosque, including a security guard whom officials credited with helping prevent additional casualties.

"The security guard played a pivotal role in keeping this from being much worse," Wahl told reporters at a news conference.

As officers searched the mosque and surrounding area, additional reports of gunfire emerged several blocks away. Authorities later found the two suspects, aged 17 and 19, dead inside a vehicle from apparent self-inflicted gunshot wounds, police said.

Investigators are examining whether anti-Muslim extremism played a role in the attack. According to the Los Angeles Times, investigators discovered anti-Islamic writings, hate-related material and a suicide note referencing racial pride inside the suspects' vehicle. Authorities also believe at least one of the firearms used may have come from a parent's home.

The Federal Bureau of Investigation is assisting local police in the investigation, which authorities said is being treated as a hate crime inquiry.

The Islamic Center of San Diego, one of the region's largest mosques, also operates an accredited Islamic school. Police evacuated students and staff during the incident, and community leaders later confirmed that no children were injured.

"This is obviously very alarming," said Deana Helmy, chair of the Islamic Shura Council of Southern California. "This is a house of worship. There's a school with children there who are trying to learn."

Taha Hassane, imam of the mosque, said the shooting had deeply shaken the local Muslim community.

"We have never experienced tragedy like this before," Hassane said. "It is extremely outrageous to target a place of worship."

The attack occurred at the beginning of Dhu al-Hijjah, one of the holiest periods in the Islamic calendar, during which Muslims around the world prepare for the Hajj pilgrimage and Eid al-Adha celebrations.

Civil rights groups, including the California chapter of the Council on American-Islamic Relations, said they are working with mosques statewide to review security measures following the shooting.

California Governor Gavin Newsom and San Diego Mayor Todd Gloria said they had been briefed on the incident and thanked first responders for their efforts.

Authorities said the investigation remains ongoing as police seek to determine the full circumstances and motive behind the attack.

Agencies contributed to the story.