An 18-year-old North Braddock man playing video games with three longtime friends inexplicably turned a gun on the group Wednesday evening, shooting two of them to death, police said yesterday.

Allegheny County homicide detectives moved quickly on the case, arresting Erskine Smith yesterday at a girlfriend's home in McKeesport and charging him with the double homicide of Jonathan Hutson, 19, and Daniel Underwood, 17.

A fourth young man was in the house at the time of the shooting but he was uninjured and did not face charges, police said. Investigators did not release his identity.

Allegheny County police Assistant Superintendent James Morton said the shootings happened at Mr. Hutson's residence in the 700 block of Baldridge Avenue between 6:45 p.m. and 7:15 p.m.

The four were playing "Madden 2006," a PlayStation2 football video game, when a minor squabble broke out. Police said they did not know what the argument was about.

"It seemed to be OK," Assistant Superintendent Morton said. "Then all of a sudden, something went wrong."

Police said Mr. Hutson died in his rear bedroom and Mr. Underwood was shot near the front door, as if he were trying to escape.

The front door was latched from the inside, and police speculate Mr. Smith left through the back.

An autopsy by the coroner's office determined that both victims died from multiple gunshot wounds of the head.

Police said Mr. Hutson spoke with his mother, Tracey Pollard, at work at about 6 p.m. and told her who was at the house. He then spoke with a cousin at 6:45 p.m., allowing police to narrow the time frame of the shooting between then and when Ms. Pollard arrived home.

North Braddock police Officer Thomas Ninehouser said Ms. Pollard walked into her house, saw a man lying on her floor and went back outside to call police.

Officer Ninehouser, who was right around the corner from Ms. Pollard's duplex, arrived almost immediately. He walked into the house and saw the body of Mr. Underwood.

Homicide detectives arrested Mr. Smith at 10:55 a.m. in the 1500 block of Soles Street. Police did not recover a weapon, but found six shell casings in the house.

In addition to two counts of homicide, Mr. Smith was charged with a gun offense and two counts of robbery for allegedly stealing cash and the video game console.

Mr. Hutson and Mr. Underwood were the third and fourth homicides this year in the borough of 6,400 residents. Two previous killings are unsolved.

In April, Mack Hoots Jr., 29, of East Pittsburgh, was shot and killed at The Place To Be bar on Sixth Street. In August Howard Milligan, 29, of Mount Oliver, was found shot to death in a narrow walkway between an abandoned building and vacant lot off Seddon Avenue.

North Braddock police Lt. Dean Bazzone said the department has been very busy this year with shootings, not just in his borough but in neighboring Braddock.