A 16-year-old boy who allegedly shot his friend while handling a gun in March was charged as an adult this week with murder, according to charges filed in court.

James Trueblood Jr., a student at Service High School, has been charged with second-degree murder and manslaughter in connection with the March 5 death of Brenton Buckmaster, 15, according to court documents.

Police say a newly purchased .357-caliber revolver Trueblood was pointing at Buckmaster went off that evening as he manipulated it in the Trueblood residence on Rainbow Avenue. The round passed through Buckmaster's chest, killing him.

The charges, filed Wednesday, accuse Trueblood of knowingly engaging in conduct that caused Buckmaster's death "under circumstances manifesting an extreme indifference to the value of human life," according to court papers.

"It wasn't intentional," homicide Detective Sgt. Slawomir Markiewicz said. "He's not charged like with first-degree murder, but of course there was an incident that cost a young boy his life."

According to an affidavit filed in court by homicide Detective Mark Huelskoetter, Trueblood and his father, James Trueblood Sr., went to a gun shop that day to trade an old .32-caliber pistol and some cash for a .357 Colt Lawman revolver.

When they got home, two friends, including Buckmaster, were there, and Trueblood took them to his bedroom to show off the new gun, charges say. All three handled the unloaded weapon, then the friends went back to the living room to play video games. Trueblood, however, went to his father's bedroom.

Though there was no .357 ammunition in the home, there were American Eagle .38 special rounds, which fit a .357 revolver. Trueblood Sr., who was in his bedroom watching TV, told police he saw his son loading and unloading the revolver but that he didn't know what his son did with the ammunition when his son left the room. The boy told police he thought the weapon was unloaded when he returned to the living room.

Buckmaster was lying on the couch as the other friend played a video game. Trueblood Jr. told police he leaned over the back of the couch, gun in hand. It was only inches from Buckmaster's back as he repeatedly cocked and uncocked it -- pulling the hammer back, then pulling the trigger with his thumb holding the hammer to ease it home, according to the charges.

"He said that the last time he hit the trigger and the gun went off. He said it was a total surprise," Huelskoetter said in the affidavit. "(Buckmaster) said, 'What the (expletive)?' then fell to the ground. James Trueblood Jr. put the gun on the kitchen table and got a towel to stop the bleeding."

Trueblood Sr. ran out to find "pandemonium" unfolding and called 911, the charges say.

The .38-caliber bullet pierced Buckmaster's left side, clipped both lungs and his heart, then exited his right side. The round went through the couch cushions and lodged in the floor. Buckmaster was taken to Alaska Native Medical Center, where he was pronounced dead.

Trueblood, his sister and father, talking to police, all characterized him as knowledgeable about guns, having fired them on ranges a number of times. In an interview with detectives, Trueblood Jr. was able to discuss different types of weapons and gun safety rules, including that one should never point a gun at anything unless planning to shoot, the charges say.

Reached at home Thursday evening, James Trueblood Sr. declined to discuss the specifics of the case, citing the pending litigation.

"It's an all-around tragedy for both sides," Trueblood Sr. said. "They were best of friends. You know, they never had an argument. Brenton was always welcome here. He spent a lot of time here and we're all deeply saddened and, you know, destroyed by this."

Nobody answered the door at the Buckmaster residence Thursday evening.

Asked if there could be any other charges in the case, Markiewicz said, "I do not believe so at this time. I think the grand jury looked at the totality of the case and this is the indictment they returned. So I don't foresee any other charges coming out."

Trueblood Jr. was arrested Wednesday and released on $2,500 bail to his father's custody.