Gunmen opened fire inside Iran’s parliament building Wednesday as a near-simultaneous suicide bomb reportedly detonated at Ayatollah Khomeini's mausoleum—a shrine to the man who launched the Islamic Revolution in 1979. At least 12 people have died and 42 more were wounded in the twin attacks, according to state media. A social-media account affiliated with ISIS declared responsibility for the attacks—the first major assault claimed by the hardline Sunni Muslim terror group inside Shiite Muslim-majority Iran. Gunmen reportedly stormed the parliament building; lawmakers were put on lockdown in the parliament’s hall, according to the near-official Tasnim news agency. The assailants were reportedly armed with AK-47s and pistols. More than two and a half hours into the assault, an explosion went off on the fifth floor of the parliament, Tasnim reported. Officials at parliament declared the situation under control shortly after noon local time, with Iranian media reporting four gunmen have been shot dead by police.