“The decision to not intervene at the time was based on protecting the safety of the large majority who were acting peacefully, and the safety of the officers,” the statement reads. “Our folks were more than ready to decisively engage had we witnessed assaultive behavior or damage to the building or surrounding property that could jeopardize its security or public safety.”

“Beyond the removal, attempted destruction of the U.S. flag, replacement of the flags, and some signs and poles being put on the main doors and windows, the protesters did not engage in behavior that warranted immediate intervention,” Metz’s statement reads.
It seems the Aurora police did not want to treat this like a combat situation either. The police chief goes on to say that the barriers he recommended were not used.

The Colorado Immigration Rights Coalition issued a statement about the incident, calling the people responsible for removing the flags “rogue protesters.”

We unequivocally denounce the actions of rogue protestors who stormed the for-profit detention camp and replaced the American flag with the Mexican flag yesterday.
I'm not inclined to believe that statement right now. The police are looking for cell phone video as part of their investigation.