Agents from the FBI and the US Marshal Service killed Reinoehl during an attempt to apprehend him in Lacey, Washington, about 120 miles north of Portland.
According to The New York Times, the US Marshals are claiming that Reinoehl shot at agents as they attempted to capture him.
"Initial reports indicate the suspect produced a firearm, threatening the lives of law enforcement officers," the US Marshals said in a statement. "Task force members responded to the threat and struck the suspect who was pronounced dead at the scene."
Agents tracked Reinoehl to an apartment complex. Reinoehl left the building and allegedly entered a vehicle. At that point, agents attempted to apprehend him.
Law enforcement agents claim Reinoehl drew a weapon while he was attempting to flee. As a result, the agents shot and killed Reinoehl.
Lieutenant Ray Brady of the Thurston County Sheriff's Office said that while Reinoehl did have a gun on him, he said "we are not able to confirm at this time if he fired shots."
An arrest warrant was issued for Reinoehl on 29 Aug. On the same day, Vice News published an interview with Reinoehl in which he claims he "had no choice"in the shooting, as he was defending the life of his friend.
The man Reinoehl was accused of killing was Aaron J Danielson. Mr Danielson was wearing a "Patriot Prayer" hat at the time of the incident, which suggests he was a member of the far-right organisation.
Patriot Prayer is an ostensibly Christian far-right organisation that had brawled with left-wing protesters in and around Portland for years.
"Over the past three years, the group has hosted and promoted rallies in progressive cities like Portland, frequently engaging in violence against their political opponents," the Southern Poverty Law Centre said in a report. "Patriot Prayer rallies regularly include the Proud Boys, a hate group, and various antigovernment extremist groups."
Reinoehl - who once wrote "I am 100% ANTIFA on his Instagram page - said he previously provided security during Black Lives Matter protests. He told Vice News that he thought Mr Danielson was going to stab him and his friend.
"I could have sat there and watched them kill a friend of mine of colour. But I wasn't going to do that," Reinoehl said.
Reinoehl was a nightly fixture at the Portland protests. He was shot in the arm while attempting to wrestle a gun away from a right-wing protester during a fight. He was also arrested for carrying a loaded gun and for resisting arrest on another occasion.
"Nightly, he would break up fights," Randal McCorkle, a regular attendee at the demonstrations and a friend of Reinoehl said. "He wanted change so badly."
Teal Lindseth, a main organiser of the protests in Portland, said he was "literally a guardian angel."
Before his death, Reinoehl said he and his attorneys were considering a a self defence argument once he turned himself in to authorities.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies