A billboard advertising campaign using a photo of Native Americans to protest gun safety laws in Colorado has brought criticism from Native American residents.

KUSA-TV reported on Monday that the ad, which shows three Native American men with the message, "Turn in your arms. The government will take care of you," is featured on two billboards near Greeley, Colorado, about 50 miles north of Denver.

Lamar Advertising, the company that owns the billboard, said the two-week ad was bought by a group that wishes to remain anonymous.

"I think it's a little bit extreme, of course," said Matt Wells, an account executive with Lamar. "But I think people are really worried about their gun rights and what liberties are going to be taken away,

But while Wells said he had not heard any complaints, some residents, like Kerri Salazar, are indeed upset about the billboards.

"You don't do this," Salazar said. "You don't take something that is indicative of an ethnicity and use it to prove your point. It is just not acceptable. No matter what the ethnicity, no matter what the point, you don't do it."

Another resident, Maureen Brucker, told the Greeley Tribune she thought it referenced the 1890 massacre of more than 150 members of the Sioux tribe at Wounded Knee in South Dakota.

"I thought it was pretty cowardly that someone would put something like that up and spend the money for a billboard but didn't have the courage to put their name on it," Brucker said of the group behind the billboards.

Watch video of the mysterious billboards, posted by CNN on Tuesday, below.