Authorities promised Sunday to pursue criminal charges after a massive party near the University of Colorado in Boulder devolved into a violent confrontation with police that left three officers injured.
Hundreds of people flooded the streets in an area known as the Hill on Saturday night and when told to leave threw bottles, rocks and other objects at police and firefighters, police said.
At least one car was damaged when the mob flipped it over, and police brought in a SWAT team and used tear gas to break up the crowd that numbered 500 to 800 people at its peak, said Boulder Police Chief Maris Herold.
Images shared by local media showed no social distancing and most without masks despite the coronavirus pandemic. Fireworks were set off in the middle of the street and a law enforcement armored vehicle and a fire truck were damaged, according to police and local media.
At one point Herold said a "tactical decision" was made to withdraw some officers when a group of about 100 people started to rush them. It took more than three hours to disperse the crowd, according to a timeline she provided.
Boulder County District Attorney Michael Dougherty described the rowdy behavior amid the coronavirus pandemic as "shameful."
"I hear people refer to it as a party. I don't regard flipping over a car as a party and I don't regard people who throw bottles and rocks at firefighters and police as a party," he said. "Those are criminal acts and will be treated as such."
No arrests were made at the scene, police said.
Officers were reviewing officer body camera footage and shared social media videos and photos to identify the individuals involved. They also set up a portal on the city's website to allow the public to submit additional video footage or other evidence from the disturbance.
Herold said it was a calculated call not to make any arrests immediately, out of worry that sending in officers would agitate the large crowd. She added that the department had "excellent" video to help it pursue those responsible for the violence.
The three injured officers were recovering, including one who was struck in the hand and another who was hit in the face but was wearing a gas mask, Herold said. City vehicles suffered thousands of dollars in damages and private property also was harmed, she said.
The Hill neighborhood has been known for decades for sometimes raucous parties and there have been previous confrontations that resulted in violence, including 12 officers injured in a 1997 riot near the school.
But city officials said during a Sunday press conference that the stakes from Saturday's events are particularly high amid the pandemic, with potentially dire consequences. Health officials advised anyone who participated to quarantine for at least 10 days and to get tested for COVID-19.
CU Boulder students returned to campus for hybrid and in-person learning in mid-February.
University officials apologized to Boulder residents who live near the school and said students who were involved in violence, property damage or failing to disperse would be held accountable.
"If they can't meet our expectation, they are not welcome at the university," said CU Boulder Chief Operating Officer Patrick O'Rourke. He added that the university knows its students were involved and "We are not going to try to shift the blame."
After the party broke up, other students came to the scene with garbage bags to pick up the large amounts of trash left behind.