Don Geer can’t understand why police killed his son, even though he watched the climax of the standoff unfold on a Springfield cul-de-sac Thursday.

John Geer, 46, was distraught that his girlfriend, the mother of his two children, had decided to leave him, so earlier that day he had thrown her belongings out of their townhouse, his father said. She called police and told them that he had a firearm.

When officers arrived, they began negotiating with Geer to come out of the home, but he refused. Don Geer was too far away to hear the conversation, but he said that at some point, his son stood with empty hands resting near the top of a screen door while several officers were positioned on the front lawn with their guns drawn.

When John Geer slowly moved his hands down about six inches, an officer fired a shot, Don Geer said. His son was hit, and he retreated into the house. A SWAT team would find him dead there just over an hour later.

Don Geer, who knew that guns were kept in the home, said he saw no weapon on his son. Neither did a good friend of John Geer’s, who gave a similar account of the shooting. They said that he could have had a concealed gun but wondered why the encounter between police and a kitchen installer with no history of violence had to end in death.

“Without having all the information, I can’t make a final conclusion, but to me, it didn’t appear a shot was justified,” Don Geer said Friday.

Police have not filled in big gaps in the case: They declined to say whether Geer was armed at the time of the shooting, why the officer opened fire and whether Geer threatened police.

“Precise movements, contents of the discussion between officer [and the] man, and all pertinent matters relating to the incident are under investigation,” police said in a written statement.

Police said the incident began about 2:40 p.m. Thursday, when they were called to a domestic dispute in the 7900 block of Pebble Brook Court. They said that officers negotiated with John Geer for about 50 minutes but that he refused to come out of the house or let them in. Geer’s girlfriend and his daughters, 13 and 17, had left by that time, Geer’s father said.

“ ‘We’re just here to help you — come out with your hands up,’ ” neighbor Edith Eshleman recalled police saying.

Jeff Stewart, the friend of Geer’s who witnessed the shooting, said the girlfriend had told him that Geer had a weapon in the house.

The incident drew a large police presence, neighbors said, with K-9 units and a helicopter buzzing overhead in addition to the SWAT team. After Geer was shot, police said, he closed the front door and remained inside. After trying unsuccessfully to get him to come out, police rammed the front door with a hostage-rescue vehicle about 4:30 p.m. and the SWAT team went inside, where Geer was found dead.

Stewart said that Geer could be stubborn and sometimes lost his temper but that he was a good man. Neighbors recalled him as even-keeled, outgoing and helpful.

A search of police records in Fairfax County showed that Geer was found guilty of drunken driving in 2010 but no convictions for violent crimes or more serious offenses.

Stewart said he talked to Geer in the minutes before the police encounter. He said that Geer didn’t say anything suicidal but he was deeply shaken about the impending breakup.

“He was emotionally wrecked that day,” Stewart said.