PHOTOS: Occupy Denver protests
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"What you saw is more of a responding to a call for help because officers were being assaulted," said Lt. Matt Murray, Denver Police.
Denver Police say they knew there was going to be a protest on Saturday and wanted to keep the event peaceful. Officers say the protesters wanted protest inside the capitol, which is illegal.
Of the 20 arrested, police say two were arrested for assaulting police officers, possible felony charges.
"We did have an officer who was pushed off his motorcycle and we had two officers who were kicked," said Murray.
Officers say the incident escalated after police tried to stop protesters from putting up tents in front of the capitol.
"The police started tearing down the tents and one guy, he just refused to leave," Chris Orchard, a witness at the protests, said. "Police said get back, but you know, they just kept moving forward. Finally, the police just took out the mace."
DPD says officers used "non-lethal agents," like mace and paintball-like balls full of pepper spray, to subdue the crowd.
"All we're trying to is have a peaceful protest and they're attacking us," said Sean Drigger, protester.
After police converged and started making arrests, officers say the crowd started to push in on them. They say the crowd even more agitated, spurring Denver Police to bring in more officers in riot gear.
Some protesters say police escalated the situation unnecessarily.
"They asked us to take a tent down. Some kid was standing too close to them. They just started attacking everybody. Spraying people with mace, arresting them. We did nothing," said Drigger.
Officers say the protesters settled down when police were able to form a circle and separate the crowd.
"We're hoping that our presence and our lack of animosity and aggressiveness will just calm everything down and people will go about their business," Murray said.
Murrary says there no reports of serious injuries, but one of those arrested was taken to the hosptial to be treated for minor injuries.
(KUSA-TV © 2011 Multimedia Holdings Corporation)