Abdul Razak Ali Artan, a Somali immigrant, was shot and killed by a police officer on Monday after he had injured 11 people by mowing them down by a car and then slashing bystanders with a butcher knife.
This comes after an analysis of Artan's social media accounts, his electronic devices as well as interviews with his family, friends and co-workers.
Artan described how he was 'at boiling point' and 'just couldn't take it anymore' in a Facebook rant, minutes before launching his brutal attack which is now being investigated as terrorism, the Daily Mail reported.
"I am sick and tired of seeing my fellow Muslim brothers and sisters being killed and tortured EVERYWHERE," he had written. "By Allah, I am willing to kill a billion infidels in retribution for a single disabled Muslim."
In the post, Artan also praised American-born Al Qaeda leader Anwar al-Awlaki, who was killed in a CIA drone strike in 2011 and has been cited as the inspiration for many terror attacks on American soil.
On Tuesday, ISIS claimed responsibility for the attack, calling Artan one of their 'soldiers'. But there has been no evidence thus far that Artan praised the group.
Born in Somalia, Artan moved to a refugee camp in Pakistan in 2007 with his mother and siblings before getting entry to the US as refugees in 2014.