In Colorado, police said that the man who opened fire at a remote active shooter training range in Boulder, Colorado, had been shot by the man standing nearby.
He was not hurt.
But the suspect is being held in custody in Boulder and is expected to face more charges.
The incident unfolded on Friday at the Boulder Active Shooter Range, a small training area that was set up by the state to train people in self-defense.
It was opened to the public.
The suspect had not fired a shot at anyone when he opened fire.
The shooting happened after a short conversation between the man and a fellow shooter, who he had been chatting with.
The Boulder Police Department told Al Jazeera that the suspect, identified as a 34-year-old man, was a licensed firearms instructor, who had been on paid administrative leave from his job as a military police officer in Colorado Springs.
The officer who opened fired, however, was not on paid leave.
The shooter, identified by police as Joshua Larimer, was shot twice in the back and the chest, according to witnesses.
Police said that a male suspect approached the shooter and asked him to show his hands.
He said he was carrying a weapon and asked for a warning before opening fire.
A man in his 40s told the shooter he was going to shoot him.
He then opened fire on the man, police told AlJazeera.
“He came up to me, grabbed my rifle, and fired a round into the air, and he turned and ran,” witness Michael P. Johnson said.
The man who had fired a warning shot returned fire, striking Larimer.
He then shot himself in the chest.
He is currently in critical condition.
Al Jazeera’s Sarah Hensher reporting from Colorado Springs, Colorado said that Larimer was a trained shooter who had just been promoted from a military service to the police department.
“We know he was an active shooter,” Johnson said, “and it seems like he got the warning shot from the military.
But we don’t know what the warning was.”
Larimer had been employed by the Colorado Springs Police Department for four years, according the department’s website.
He had served in the Air Force from 2005 to 2011, according a post on his Facebook page.
Johnson said that while he had seen Larimer on his police report, he had never seen him carry a weapon before.
“I didn’t know who he was,” he said.
“But he seemed pretty normal, and then he got shot.”
Johnson said he had heard people in the area talking about Larimer before.
The Colorado Springs police department said that they were working to find out more about Larimers background, but declined to comment further.
Larimers family has not been able to speak with the media.