A call to deal with “a man with a gun” is one of the most dangerous that police officers face. Entering an unpredictable situation, they are trained to act to protect their own safety and the public’s.

When the suspect is a soldier, the situation grows more complicated. In Gresham, Ore., a veteran was killed by the police when he stepped out onto his front porch carrying a rifle; his family had called 911 saying he was suicidal. In Glendale, Ariz., a soldier newly returned from Afghanistan shot a man in a bar and then fired at a police officer, who killed him.

Officer John Free was the first to respond to Mr. Eifert’s house that night. As he crouched with his AR-15 rifle behind the pine trees across the street waiting for a clear shot, he said, he thought of his 7-month-old daughter and wondered if he would see her first birthday. He saw muzzle flashes in the darkness and heard bullets whiz through the trees.

“Your mind plays tricks on you when you’re out there for 2 1/2 hours in the dark,” he said. “You would hear something in the woods and it would turn out to be a deer, and then O.K., it’s just a deer, but is the deer moving because he’s moving towards us?”

Officer Free took off his reflective badge and smeared mud on the illuminated dial of his radio. At one point, an officer crawled across a hornet’s nest, and when a sharp pain went through his leg, he thought he had been shot.

Still, when Ms. Emerson called Officer Free to ask about the charges, he said he bore Mr. Eifert no hard feelings.

“I said, ‘I don’t think any of us would not want him to get treatment,’ ” he said.

“There’s a difference between somebody who’s a criminal and someone who’s just in a perfect storm of things going wrong.”