As Monday became Tuesday morning, two friends shared an uneventful night in Munhall.
They drank at local bars and went home around 3 a.m. before deciding to go out again for a walk and a smoke.
As they turned down an alley and walked past a garage, Allegheny County police said, the men decided to sneak inside through a door panel.
Moments later, one of them, Andrew E. Stevens, 23, raised a handgun and shot at the garage's owner, police said, and was killed by the owner's return fire.
Munhall's acting police chief, Sgt. Joseph A. Cibula, identified the homeowner as John Rozgonyi, 58.
Neighbor David Pigott said the shootout happened quickly.
"I can't believe that he wasn't shot," he said of Mr. Rozgonyi. "They were shooting that fast at each other."
County police are seeking more information about Mr. Stevens, a former noncommissioned officer in the Marine Corps who went to Steel Valley Senior High School, according to his Facebook page.
His companion, Shaun Conroy, 24, was charged with burglary and conspiracy to commit burglary.
The shooting started shortly before 3:30 a.m. Tuesday after neighbors called Mr. Rozgonyi and said someone was in his detached garage on Victor Way, behind his home in the 100 block of East Eugene Avenue.
County police said Mr. Conroy entered the garage and Mr. Stevens acted as a lookout outside.
Sgt. Cibula said Mr. Rozgonyi went outside and told Mr. Stevens that 911 had been called and police were on the way.
"[Mr. Stevens], according to independent witnesses, began firing his weapon at the homeowner, who then fired his weapon in self-defense," county police said in a news release.
Neither Mr. Rozgonyi nor his girlfriend, who was with him at the home, was injured, police said. The girlfriend's daughter also lives there.
When he heard the commotion outside the garage, Mr. Conroy ran out and tried to get away, but police quickly caught him.
It doesn't appear that the two men knew Mr. Rozgonyi, Sgt. Cibula said.
County police don't plan to charge Mr. Rozgonyi, but the case will be reviewed by the Allegheny County district attorney's office. Mr. Rozgonyi legally owned the handgun and had a permit to carry it, county police said.
Police also spoke with a third person Tuesday, a man armed with a gun who came within a block or two of the scene after hearing the events on a police scanner. He had a carry permit for his gun and will not be charged, police said.
Friend Drew Blasko said Mr. Stevens left the Marine Corps in June, after serving four years -- including at least six months in Afghanistan -- and had enrolled at the Community College of Allegheny County.
Mr. Blasko said the actions police allege are uncharacteristic of the "good kid" he remembered from high school. "I was really surprised," he said.
Molly Born: firstname.lastname@example.org, 412-263-1944 or on Twitter @borntolede. Lexi Belculfine contributed.