By Matt Kroschel

STEAMBOAT SPRINGS, Colo. (CBS4) –  As dozens of families peacefully protested with thousands others across the country on Saturday, at least one person passed by the crowds in Steamboat Springs “rolling coal.”

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That act is illegal under new Colorado law.

Camille DiTrani provided a photo of the incident that included the license plate number. The protesters were part of the March For Our Lives events along Main Street.

(credit: Camille DiTrani)

“They somehow tweak their engines, so they can blow out black smoke when they gas it up. They were doing that to the crowd, and my concern is there was little kids there,” Wahl said.

Witnesses say at least two trucks circled the block repeatedly to blow the black smoke on demonstrators.

Liz Wahl (credit: CBS)

“I don’t think they’re used to enforcing this law, but it’s really important because the folks were using their trucks as… maybe they’re trying to make a statement, which obviously they were. We want them don’t get out and talk,” Wahl said.

CBS4 reached out to Steamboat police to find out if a formal complaint has been filed. Police say thanks to the photograph they were able to track down the driver – 20-year-old Alex Graham from Routt County. He was issued a citation under the new law.

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(credit: CBS)

The driver of the second truck remains unidentified.

“It’s not cool. Not real for guy to be like that to all these people that are peacefully protesting,” said Kevin McReynolds.

CBS4’s Matt Kroschel interviews Kevin McReynolds. (credit: CBS)

Wahl wants to open up the dialogue with those who targeted her and fellow marchers.

“We’re a great community here. We love everyone. We love people on the right, people on the left. We love our whole community. We want to have a conversation. Don’t use your truck to have a conversation,” Wahl said.

Similar incidents were also reported by marchers in Salida Saturday.

Graham has not respond to a CBS4 request for comment.

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Matt Kroschel covers news throughout Colorado working from the CBS4 Mountain Newsroom. Send story ideas to mrkroschel@cbs.com and connect with him on Twitter @Matt_Kroschel.