HILLSBOROUGH, N.C. — Police said Tuesday that a Chapel Hill teen accused of gunning down his parents had to stop and reload the gun every time he fired.

Adam Sapikowski, who was charged Saturday with two counts of first-degree murder in the death of his parents, James and Alison Sapikowski, used a family gun, police said -- a .410-caliber shotgun -- to kill his parents.

"It's a single-shot shotgun," Chapel Hill Police Chief Gregg Jarvies said. "You have to reload before every shot."

James Sapikowski was shot three times. Alison Sapikowski was shot twice.

Both bodies were found in a first floor master bedroom, but shell casings were found in the kitchen and the breakfast nook, as well as the master bedroom and bathroom.

Jarvies, said, however, he was unable to give out any information about the crime scene.

Police are now focusing on a timeline to determine what the 16-year-old did between the time of the killings and the discovery of the bodies.

The medical examiner believes the couple died two weeks before anyone found them. Police believe the slayings happened around the weekend of Adam Sapikowski's high school prom.

"We know for certain Adam was at the prom," Jarvies said. "We've heard reports that he and some other people may have gone back to the house -- we're looking into those reports."

Investigators said Adam Sapikowski checked into a Durham hotel on May 1, the day after his prom, and stayed there off and on for two weeks.

Police also met with school administrators at Durham Academy to determine if the teen had been in school after the murders were believed to have occurred. School officials told police they could expect attendance records in the next couple of days.