ANCHORAGE, Alaska (AP) _ A store owner shot and killed a high school senior who was fleeing after trying to steal an advertising balloon as part of a scavenger hunt, police said.

Clyde Thompson, 18, was shot as he ran from a furniture store late Saturday. Friends said he died in the bed of their pickup truck while they were racing to get him to a hospital.

Authorities did not release the store owner's name. He was not charged but the case was referred to the Anchorage district attorney's office.

Thompson and a group of friends were taking part in an elaborate scavenger hunt, a spring prank among Service High School students that is not sanctioned by the school.

Many juniors and most of the senior class had gathered on the school campus to buy a list of items they had to collect to win.

''It's school tradition,'' said Heather Estabrook, 18, one of Thompson's companions. ''It's fun before our graduation.''

Among 46 items on the list were such things as a garbage bin, a wheelchair and the brightly colored, helium-filled balloon from the roof of the Lo-Mark furniture store.

Saturday evening, the 15 friends headed out in three autos with cellular telephones, said Estabrook, one of the drivers. They spotted the balloon, the last item on the list, and drove to the store parking lot just as a large motor home pulled in, she said.

Police said the store owner was dropping off his recreational vehicle.

Four of the students, including Thompson, had climbed the side of the store to the roof. Police said the store owner fired several shots and one hit Thompson in the back as he ran for the truck.

''The guy never knew he hit anybody,'' said police Sgt. Sid Moen. ''He admitted doing it, and came down to the station to be interviewed. He said he tried to scare them off by shooting into the air.''

Assistant District Attorney Steve Branchflower said he did not immediately know all the facts so could not comment on specifics.

''We'll have to take a look at the police reports and decide the reasonableness of his conduct in light of everything,'' Branchflower said. ''It's a pretty troubling set of facts and it's a real tragic event.''