Two teenage suspects who attacked the Islamic Center in San Diego on Monday, killing three people before turning the guns on themselves, were engaging with far-right extremist content on social media, authorities have said.Authorities are working to determine a motive for the attack, which is being investigated as a hate crime. The gunmen left behind a 75-page manifesto that preached hate, anti-Islam ideology, antisemitism and promoted violence. The Times also identified social media accounts, believed to be used by one of the shooters, that contained content that idolized school shootings, white nationalism and neo-Nazi terrorism and memes from the online...