The paper also reported that some in the crowd set off fireworks and flipped at least one car.
Police arrived on scene shortly before 8:30 p.m and used loudspeakers to tell the crowd to disperse or risk arrest, tear gas or use of force, the Daily Camera reported.
The crowd was dispersed around 9:30 p.m., police said.
“Detectives will review every lead we have to identify and arrest those responsible for this reprehensible and unacceptable behavior,” said Chief Maris Herold in a post from the department.
CNN has reached out to the Boulder police for comment.
The university called the gathering “unacceptable and irresponsible,” and said it is aware of allegations of “violence toward police officers.”
“Any student who is found responsible for having engaged in acts of violence toward the law enforcement or other first responders will be removed from CU Boulder and not readmitted,” the university said in a statement.
The large gathering came a day after Colorado Gov. Jared Polis extended the state’s Covid-19 mask mandate, which has been in place since July 2020. Nearly 6,000 people have died in Colorado due to Covid-19, according to data from Johns Hopkins University.