Police arrested a 33-year-old man who was participating in a protest against police brutality on Monday, accusing him of displaying a handgun in a threatening manner following a confrontation with a motorcyclist.

Rocco Wong faces one count of criminal threatening with a dangerous weapon and was taken into custody after 7 p.m. Monday.

Wong was with a group of about 10 people who were on Middle Street returning to City Hall from the Portland Police Station when they encircled a motorcyclist stopped at a stop sign on Pearl Street, police said.

The motorcyclist felt threatened by their actions, and when he got off the bike, a person encircling him lifted his shirt to show a handgun and made several threatening statements, police said. The group then returned to City Hall plaza, where they continued to protest.

The 50-year-old motorcyclist, of South Portland, met with police and identified Wong as the man who threatened him. Police waited for Wong to separate from the group and arrested him without incident. Officers seized a handgun from Wong, police said.

Wong was booked at the Cumberland County Jail and released on $250 bail.

Police Chief Frank Clark cautioned demonstrators last week to leave their firearms at home after detractors made threats against Black Lives Matter protesters in messages on Facebook, and suggested in comments online that they planned to counter-protest and to come armed.

There were no arrests at a demonstration Saturday organized by Black Lives Matter Maine, which also drew counter-protesters. A second demonstration on Sunday also did not generate any arrests, police spokesman Lt. Robert Martin said.

Black Lives Matter Maine says it supports only peaceful demonstrations, and has condemned violence in statements made on social media.

“Emotionally charged events, such as can be the case with some protests, can lead to poor decision-making, which does not mix well with firearms or other weapons,” Clark said in a statement Tuesday. “That can put the public and my officers at risk.”