Federal prosecutors have filed hate crime charges against a Pennsylvania man they say stormed a Pittsburgh synagogue and opened fire, killing 11 people... He made anti-Semitic statements during the shooting and targeted Jews on social media, according to a federal law enforcement official... The attack is believed to be the deadliest on the Jewish community in US history, the Anti-Defamation League said in a statement... Bowers is charged with 11 counts of using a firearm to commit murder and multiple counts of two hate crimes: obstruction of the exercise of religious beliefs resulting in death and obstruction of the exercise of religious beliefs resulting in bodily injury to a public safety officer, authorities said, citing a sealed criminal complaint. 

... A law enforcement source told CNN that investigators believe an account on Gab, a social media platform, that espoused anti-Semitic views belonged to Bowers... Bowers' anti-Semitic comments also fueled other hate speech he shared on Gab, which has styled itself as an alternative to Twitter and puts nearly no restrictions on content... Bowers also posted photos on his Gab account showing his handgun collection, including multiple magazines and sights... In a statement, Gab disavowed "all acts of terrorism and violence" and said its mission was "to defend free expression and individual liberty online for all people."