Twin Falls, Idaho - A gunman opened fire at a fast-food restaurant in Idaho on Saturday, killing an as yet unknown number of people, police said, adding that the suspect was also dead.

The shooting at the In-N-Out Burger restaurant "resulted in fatalities," but authorities said that they were still working to determine the number of victims.

"It was a very chaotic scene," Twin Falls Police Chief Matthew Hicks told reporters.

Twin Falls city spokesman Josh Palmer told NBC News that three people had been killed and at least two more were wounded, but that it was not clear if the gunman had been counted among the reported casualties.

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Video footage aired by local media outlets showed what appeared to be a young man with a long gun outside of the In-N-Out Burger location.

Other video posted on social media showed more than a dozen people running out of the restaurant.

Twin Falls is a city of about 56,000 people in southern Idaho, about 180 miles northwest of Salt Lake City.

Lynsi Snyder, owner and president of In-N-Out, later released a statement on the shooting.

"My heart is broken, my chest is heavy, my eyes burn from the tears I've shed," she wrote. "IN-N-OUT will be mourning with the families and praying for them... we will stand together."