The Portland Police Department said several thousand demonstrators marched peacefully until about 11:30 p.m. local time when some protesters began to throw projectiles at officers.

“After the crowd fractured into smaller groups, for about two hours, demonstrators set fires, smashed store front windows, vandalized buildings, and parked vehicles. Officers made arrests and continued to disperse the small groups,” police said in a news release.

At least 12 adults were arrested and two juveniles were detained, police said.

“It has been a long, difficult and emotional several days in Portland and across the country and we understand why,” Police Chief Jami Resch said in the news release. “Yesterday’s events started peacefully and there was a very organic moment when some of our Sergeants and demonstrators took a knee together next to the Justice Center. I am proud of this moment, as it reflects community and understanding.”

Resch said while she was meeting with several demonstration leaders, some protesters began to act violently.

“Officers deployed riot control agents to disperse the crowd for the safety of all,” police said in the news release.