As his father napped one evening last summer, prosecutors said, Richard Hanson grabbed a pistol from the top of a cabinet in their Springfield home, walked into the bedroom and fired five shots into the man’s face.

The son pulled the bedroom door closed. Then he drove to 7-Eleven to buy a six-pack of beer and some scratch-off lottery tickets before fleeing the state, witnesses said.

On Thursday, a Fairfax County Circuit Court jury found the 54-year-old Army veteran guilty of first-degree murder in the killing of Gary P. Hanson and of a related firearms charge. They recommended a sentence of 25 years in prison.

Prosecutors were at loss for a motive, and the crime stood in stark contrast to the “gentle giant” whom family and neighbors described on the stand and vowed to support while he was in prison.

“This defendant killed his father in cold blood,” said Assistant Commonwealth’s Attorney Robert D. McClain. “What makes this killing all the more terrifying is that we don’t know why.”

Richard Hanson pleaded not guilty, and public defenders Vernida Chaney and Diego Alcala Laboy said he suffered from a drinking problem. They described him as a “caregiver” who babysat for neighborhood children, helped his mother with gardening and took his father on golf outings.

“These actions were horrific, and many lives were affected in this courtroom,” Alcala Laboy told jurors after they returned the verdict. “These acts are not Richard Hanson.”

Curtis Hanson, Richard Hanson’s younger brother, testified in the trial that he had clashed with his brother on July 19, the day of the killing, at the home on Chancellor Way they shared with their parents. It appeared his brother had been drinking, he testified, and things became so heated that he contemplated shooting him.

Curtis Hanson and the brothers’ mother, Rosalinde, left for a dentist’s appointment shortly before 5 p.m., he testified. A short time later, prosecutors said, Richard Hanson shot his father, a retired lawyer with the Veterans Administration. The son fled in his family’s green Saturn with his father’s wallet, the murder weapon and insulin to treat his diabetes.

Curtis and Rosalinde Hanson arrived home to find Gary Hanson, 75, fatally shot. In a 911 call played in court, Curtis Hanson identified his brother as the likely killer. His mother could be heard crying in the background.

“I cannot believe that son of a [expletive],” he told a dispatcher.

Richard Hanson was arrested two days later at a Red Carpet Inn in Scranton, Pa. Prosecutors said the .45-caliber Glock handgun he used to shoot his father was found in the trunk of the Saturn.

Richard Hanson didn’t take the stand, and during the trial, the defense rested without calling a witness. Hanson was unemployed at time of the shooting, but he had once been employed by Fairfax County as a maintenance worker.

Before the jury made its sentencing recommendation, Curtis and Rosalinde Hanson and neighbors took the stand to speak on behalf of Richard Hanson.

Rosalinde Hanson said the family was “close-knit” and described how Richard and his father watched football together. They said they talked to Richard regularly after his arrest and put money in a jail account for him.

“I still love my brother unconditionally, despite what the facts are,” Curtis Hanson testified.