A Springfield man who was killed by a Fairfax County police officer during a standoff at his home Thursday was not carrying a gun at the time of the shooting, but one was found nearby afterward, his father said a detective had told him.

John Geer, 46, was shot after officers tried, without success, for 50 minutes to persuade him to leave his Pebble Brook Court home, police said. Officers had been called to the scene by Geer’s girlfriend, who police said had reported that he was armed.

Geer’s father, Don Geer, was outside the home as officers talked with his son. He has said he watched as his son stood with empty hands resting on top of a screen door at the front door. When John Geer lowered his hands about six inches, his father said, one officer opened fire, and John Geer was hit. He retreated into the home, where a SWAT team later found him dead.

Don Geer said Tuesday that a detective investigating the case told him that his son was not holding a gun at the time of the shooting and that he did not have one on his person. Geer said the detective told him that officers found a holstered handgun on a stairway landing that is a “couple of steps” from the front door.

Geer said the officer should not have shot his son.

“If he doesn’t have a weapon in his immediate possession, the officer should not have fired,” Don Geer said. “He would have to have turned around, bent over and then picked up the gun to present a threat. It’s pretty hard to say the shooting was justifiable.”

Geer said he could not hear the conversation between the officers and his son before the shooting. He said the detective declined to say what had transpired.

County Police Chief Edwin C. Roessler Jr. expressed his condolences Tuesday for John Geer’s death, but he declined to comment on the facts of the case. “My commitment is that a thorough investigation will be conducted,” he said.

Police have not said whether John Geer was armed or why the officer opened fire, and they have declined to discuss the conversation between John Geer and the officers before the shooting.

On the day of the shooting, John Geer was distraught that his girlfriend — the mother of his two teenage daughters — planned to leave him, and he had been throwing her belongings out of the house, his father said.

John Geer, a kitchen designer and installer, had never been convicted of a violent crime in Fairfax County.