Reports say police shot Michael Reinoehl in Lacey, south of Seattle in Washington state
Michael Reinoehl, 48, was being investigated for the killing of a supporter of President Trump during last weekend’s tension.
Reinoehl earlier said he acted in self-defence when he shot Aaron Danielson, a member of the Patriot Prayer group.
Police said he was armed and was shot during a confrontation with officers.
Last Saturday Trump supporters held a large rally and fought with anti-racism protesters in violent exchanges.
Black Lives Matter protests have been taking place nightly in Portland since the killing of black man George Floyd in May.
Reinoehl, who regularly attended the protests, had told Vice News that he had thought he and a friend were going to be stabbed by Danielson.
“I had no choice. I mean, I, I had a choice. I could have sat there and watched them kill a friend of mine of colour. But I wasn’t going to do that,” he said.
On Thursday President Trump had highlighted the killing of Danielson, tweeting “Why aren’t the Portland police arresting the cold blooded killer of Aaron “Jay” Danielson. Do your job, and do it fast.”.
A warrant for Reinoehl’s arrest was issued and he was located by agents on Thursday in Lacey, Washington about 120 miles (193km) north of Portland.
Thurston County Sheriff’s Lieutenant Ray Brady said it was not clear why the suspect was in Lacey and he did not believe the suspected lived at the address.
Lieutenant Brady said the police were conducting surveillance when the suspect left the apartment and got into a vehicle in the road.
“There was a confrontation between the officers that were on scene and the subject,” he said.
“The information we have at this time is that the subject was armed. There were shots that were fired into the vehicle and the subject fled from the vehicle, at which time there was additional shots that were fired.”
He said four officers fired their weapons.
Reinoehl was suspected of shooting Danielson during clashes on Saturday night when a large procession of supporters of President Trump clashed with Black Lives Matter protesters.
The shooting came amid fights between the Trump supporters and BLM protesters in the city centre.
Video showed some people firing what local media described as pepper spray and pellets at BLM groups who had tried to prevent them entering the city by blocking streets.
The city has become a flashpoint for tension with some violence between between far-right groups, such as Proud Boys and Patriot Prayer, and left-wing counter-demonstrators known as antifa, or anti-fascist movement.
“I am 100% ANTIFA all the way!” Reinoehl posted on Instagram in June and he suggested that the counter-protestors’ tactics amounted to “warfare”, according to US media.
In July he was told to appear in court on charges of carrying a loaded gun in public and resisting arrest.
On 26 July he told AP that he had been shot in his arm after intervening in a fight between an armed white man and a group of young black people.
On Thursday Oregon Governor Kate Brown and Democratic officials condemned the violence that had taken place in Portland, writing “The violence must stop. There is no place for white supremacy or vigilantism in Oregon.