The two teenage suspects in the gun attack on a San Diego mosque shared a "broad hatred" of multiple religions and racial groups, authorities have said.

Five people, including the two attackers, died in the deadly violence on Monday.

Authorities have not disclosed a motive for the attack, but San Diego's police chief said the violence was being investigated as a possible hate crime.

The suspects were found dead of apparent self-inflicted wounds in a vehicle blocks away from the mosque, police said.

What was the timeline of the attack?

Authorities said they responded to a report of an active shooter at the Islamic Center of San Diego at 11:43 local time on Monday.

San Diego Police Chief Scott Wahl said officers arrived four minutes later and found three men dead outside the mosque.

As officers began active shooter protocols, they received another call that shots had been fired nearby from a vehicle at a landscaper. The landscaper was not struck.

Police Chief Wahl said the mother of one of the two alleged attackers had called police around 09:40 local time to report that her son had run away with her firearms and her car.

She told authorities the teenager may be suicidal and could be with a friend.

The suspect's mother also told authorities that her son was dressed in camouflage.

Later, less than a quarter of a mile away, police found the two suspects - aged 17 and 18 - dead of self-inflicted wounds in a vehicle.

Who were the victims?

The three victims have been identified as Amin Abdullah, Nader Awad and Mansour Kaziha, a spokeswoman for the Council on American-Islamic Relations-San Diego (Cair-SD), Tazheen Nizam, told the BBC.

Police have said he stopped the attack from being much worse.

"It's fair to say [Abdullah's] actions were heroic," Wahl said. "Undoubtedly, he saved lives today."

A friend of the family told the Associated Press that Abdullah was well-known at the mosque and had worked there for more than a decade.

Nizam, the Cair spokeswoman, told the BBC: "Amin was loved by everybody, he stood there day after day, always smiling, welcoming everybody, welcoming the kids who came to the school.

"He was a shining light. He is a true hero, a martyr."

The children of Awad, one of the other victims, grew up in the mosque and his wife teaches at the school inside it, Nizam said.

Kaziha, the third victim, helped maintain the mosque's grounds and convenience store, the Cair spokeswoman said.

What do we know about the attackers?

Authorities have not yet released the names of the alleged attackers, though some US media have named them.

They are 17 and 18 years old, according to police.

Authorities seized more than 30 guns and a crossbow while searching three residences associated with the suspects.

The weapons - including numerous pistols, rifles and shotguns - were registered to one of the suspect's parents.

Ammunition, tactical gear, and mobile phones belonging to the teenagers were also seized.

The shooting is being investigated as a hate crime, Wahl said, noting that "hate rhetoric" was involved.

A search of the suspect's car found "writings and various ideologies outlining religious and racial beliefs of how the world they envisioned should look," FBI Special Agent Mark Remily said. "These subjects did not discriminate on who they hated."

Authorities also recovered a document that suggested their "hatred covered a wide aspect of races and religions".

Wahl said on Tuesday that investigators are still trying to understand what the "intended target location" was and the scope of the threat.

The two suspects were radicalised online, authorities said, but did not elaborate on how. They said the suspects met online and later learned that they both lived in the San Diego area.