Two teenage gunmen opened fire on Monday at the Islamic Centre of San Diego, California, killing a security guard and two other men outside the mosque before the suspects were found dead, apparently from self-inflicted gunshot wounds, police said. San Diego Police Chief Scott Wahl said local law enforcement and the FBI were investigating the attack on the largest mosque in San Diego County as a hate crime. However, no precise motive or precipitating incident for the gun violence has been publicly suggested by authorities.