An Air Force pilot was assaulted with a bat in Washington state Saturday by masked “anarchists” after they noticed he was displaying two Confederate flags on his motorcycle, police said.

The incident occurred in Olympia, Wash., a few miles west of where the man is stationed at Joint Base Lewis-McChord. The pilot was stopped because protesters were marching in the street. Then they surrounded him as they attempted to knock his motorcycle over, according to a police report.

“They sprayed the victim in the face with mace, and struck him in the back with a baseball bat and a glass bottle filled with red paint,” the report said. “The victim suffered severe eye irritation and a bruised shoulder and back. One of the witnesses attempting to assist the victim was also sprayed in the face with mace.”

[The Army defends its use of Confederate military officer names on modern installations]

The attack comes following a summer in which the use of the Confederate flag was hotly contested, following the June 17 attack on a historic black church in South Carolina that killed nine people. The suspect in that case, Dylann Roof, 21, faces the death penalty, and was photographed displaying the Confederate flag before the attack.

Police said the protesters in Washington were all dressed in black and camouflage. “This protest group identified themselves as ‘anarchists,’ which is a local Hate Group,” the police statement said. “Their actions and message was violence and hatred.”

The description of the assailants was limited — police said witnesses described them as white men, one of whom was about 6-foot-4. The attack came the same day in Olympia that protesters damaged Olympia City Hall while shouting anti-police messages, according to local media reports.

Police described the damage to city hall as “extensive,” and said at least one other person was injured during the protest.

The attack on the pilot has generated widespread attention in the past 24 hours, including by the independent Air Force Times, the Daily Caller and the Washington Examiner.