A shooting at a newly opened In-N-Out Burger in Twin Falls, Idaho, on Saturday afternoon left multiple people dead, authorities said Sunday.

Twin Falls Police Chief Matthew Hicks said three people were killed and seven others were injured in the “chaotic” incident at the fast food restaurant. The suspected shooter also was dead at the scene.

“We recognize the fear and concern this has caused in our community,” Hicks said at a Sunday news conference livestreamed by local news stations.

The police chief said that at 2:29 p.m. Saturday, the department received multiple 911 calls where “dispatchers could hear screaming and reports of gunshots in the background.”

Multiple agencies converged at the scene, he said.

“First responders faced what was described as one of the most chaotic instances a law enforcement officer can face in their career,” he said.

Police identified 24-year-old Chad Williams as the attacker. Williams died from a self-inflicted gunshot wound, Hicks said.

Hicks said that previous speculation around multiple shooters was false. He said that two people, an off-duty state law enforcement officer and a local citizen, “actively engaged” Williams “by returning gunfire towards him.”

“We believe their actions helped drive the suspect away from the scene, preventing further casualties,” Hicks said.

As first responders arrived at the scene, officials closed roads around the restaurant, including the city’s famed Perrine Memorial Bridge over the Snake River. Nearby residents were ordered to shelter in place.

The FBI was assisting local law enforcement with the investigation, Hicks said.

Of those injured, two were in critical condition, two had been treated and released and there were considered stable, he said.

“Based on the best information that we have at this time, we are confident that Mr. Williams acted alone,” Hicks said Sunday. The attacker’s motivations are still under investigation.

In-N-Out revealed it would open the Twin Falls location — the sole one in the city — earlier this year, along with five other locations across California, Arizona, Utah and Tennessee. Hicks described the area as “one of the busiest locations in all of Southern Idaho.”

The company’s website lists the Twin Falls location as temporarily closed.