June 15 (UPI) — A protest outside of an Immigration and Customs Enforcement facility in Oregon has been declared a riot by the Portland Police Bureau.

Police said in a statement early Sunday morning that the massive demonstration was attended by some “tens of thousands” of protesters, and described as “peaceful” throughout the afternoon on Saturday.

But shortly before 6 p.m. on Saturday evening, a federal officer was reported to have been injured by the crowd. And around 8 p.m., police arrested 25-year-old Sabian Crisantos for an attempted assault of a public safety officer.

“Throughout the night, PPB observed criminal behavior, which resulted in targeted arrests. Officers on bikes conducted visibility patrols in an attempt to deter crime, but also recognized that at times their presence escalated the crowd,” police said.

“During those times, the decision was made to disengage, but officers remained in the area to respond to any additional criminal activity.”

Portland police said they made a second arrest just before 11 p.m. when a person was observed throwing a rock at a building. The suspect was identified as 20-year-old Tyson Kahnert, who faces a number of charges, including criminal mischief.

And a third man, 38-year-old Cory Oien, was arrested for theft and driving under the influence of intoxicants after he was seen picking up “traffic control devices” in the area and putting them in the bed of his truck around 1 a.m. Sunday morning.

They were all booked into the Multnomah County Detention Center, police said.

The scene was no longer declared a riot by 9:15 p.m.

The news came as at least one person was critically injured Saturday in a shooting at a protest against President Donald Trump in Salt Lake City and hours after two Democratic lawmakers in Minnesota were shot dead by a gunman.