A social media profile of Robert Bowers, 46, has shed light on the killer’s hate-fuelled mentality.
Mr Bowers was reported to be a regular poster on Gab, an alternative Twitter platform popular among white supremacists, white nationalists, alt-right group supporters and people who are banned from using traditional social media platforms.
Before his account was closed down, Mr Bowers was said to have denounced US president Donald Trump labelling him a “globalist, not a nationalist”, The Sunday Times reported.
He wrote: “For the record, I did not vote for nor have I owned, worn or even touched a maga [Make America Great Again] hat.”
Mr Bowers has been charged with murder after 11 people were killed at Tree of Life synagogue yesterday.
He 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, CNN reported.
If Mr Bowers is convicted of a hate crime then he could be issued the death penalty.
At the time of the attack Mr Trump wrote on Twitter: “This evil Anti-Semitic attack is an assault on humanity. It will take all of us working together to extract the poison of Anti-Semitism from our world. We must unite to conquer hate.”
He added that when such vile hate attacks occur during your own presidency “it’s a level of terribleness and horror that you can’t even believe. It’s hard to believe”, during an agricultural convention and a political rally yesterday.
Mr Bowers, of Baldwin, a borough of Pennsylvania, was alleged to have made anti-semitic statements during the shooting and made jews the focal point of his online rants.
In another message posted on Gab just hours before the rampage, Mr Bowers appeared to say the Jewish refugee organisation, the Hebrew Immigrant Aid Society, “likes to bring invaders in that kill our people. I can’t sit by and watch my people get slaughtered”.
He added: “Screw your optics, I’m going in”.
FBI special agent Bob Jones said Mr Bowers was armed with an assault rifle and three handguns when he stormed the building.
He surrendered to authorities after Saturday morning’s shooting when he was injured and was taken to a hospital where he was listed in fair condition.
Mr Trump told reporters the killings might have been prevented if there had been an armed guard at the synagogue.
He said: “If they had some kind of a protection inside the temple maybe it could have been a much more different situation, they didn’t.”
Police are normally only present at the synagogue for security on high holidays.
He called on Americans to rise above hate and ordered US flags at the White House and public buildings to be flown at half-staff.
Mr Trump is due to visit Pittsburgh but the details of his trip are unknown.
After the shooting Gab backed up Mr Bowers’ account data, closed the account and sent the information to FBI.
The names of those shot dead at the synagogue will be released today.