DENVER (KDVR) — Police say that 18 people were arrested during anti-Immigration and Customs Enforcement protests that started at the State Capitol Tuesday evening.

Police records indicate that officers believed some of the protestors were trying to make Molotov cocktails. Police arrest records show people were arrested for, among other things, obstruction of a roadway, failure to obey a lawful order, graffiti and second-degree assault of an officer.

The protest was mostly peaceful, according to Denver Police Chief Ron Thomas.

“(I’m) Disappointed, though, that there were agitators in the crowd that really wanted to try to taunt the police, create dangerous situations for the community,” Thomas said.

Tensions grew as the crowd left the Capitol grounds and headed toward Broadway and Interstate 25.

There was concern that the protestors would walk onto the interstate.

“Our first tactic was to use smoke as a deterrent and let them know that we are serious. We don’t want to continue with the activity that you’re engaged in right now. That was effective in getting a number of people to leave the area and stop their attempts to gain access to the highway,” Thomas said.

The crowds in Colorado were protesting ICE raids taking place in Los Angeles and across the U.S. A spokesperson said they wanted to show their support for protestors in California.

In one instance, arrest records show a protester scratched an officer, which led to an assault charge.

“They will be the cases that we’ll see more attention from prosecutors and courts in terms of holding individuals responsible,” FOX31 Legal Analyst Christopher Decker said.

However, Colorado 50501, which is planning the "No Kings" events for Trump's birthday, said that it did not participate in planning the march on Tuesday night, but did promote the nonviolent march and peaceful protest, "in support of immigration rights and demanding an end to the criminal executive overreach of the current administration."

The organization said that a group "splintered" at the end of the peaceful event and proceeded to protest into the evening, which 50501 said was not represenative of the group's values.

"We wholeheartedly support everyone's right to protest," the group wrote. "This fundamental freedom is a pillar of democracy and a vital expression of invidual and collective voices."

The group said it will continue to commit to nonviolence, inclusivity and conflict resolution.

DPD said pepper balls were also fired at the ground to create a deterrent and break up the crowds. FOX31 was told that many of the tactics that were used during the protest Tuesday night were implemented after the George Floyd protests in 2020.

FOX31's Heather Willard contributed to this report.