An 8-year-old boy was in critical condition Saturday after a team of surgeons worked through the night reattaching the arm he lost in a shark attack.

Three surgeons and a large surgical support team worked 12 hours in shifts to reattach the right arm, which was bitten off by what authorities believe was a bull shark.

The boy was attacked at about 8:30 p.m. CDT Friday as he swam at Gulf Islands National Seashore near Fort Pickens in the Florida Panhandle.

The boy's uncle wrestled the 7-foot shark to shore, where a ranger shot it. Emergency medical personnel then retrieved the arm, according to chief ranger J.R. Tomasovic.

"A ranger shot it in the head three times, which was enough to get the shark to loosen his jaws," said ranger John Bandurski.

He said the shark looked like a bull shark, known as being an aggressive shark.

Tomasovic said he believes the boy is from Ocean Springs, Miss., and that he had gone to the beach with his aunt and uncle. Hospital officials and other authorities refused to give any details about the family, and at the request of the family their names were not released by officials.

Family members in a waiting room Saturday declined comment other than to say the uncle, who is from Mobile, Ala., was not at the hospital.

Immediately after the attack, relatives and emergency crews struggled to revive the boy about 250 yards west of Langdon Beach at the Gulf Islands preserve.

"It looked like the shark had been feeding on him," said tourist Guy Ogburn, 44, of Nashville, who was on the beach when the boy's uncle wrestled the shark ashore.

"When I first got to him, his arm was off, his leg was wide open and there was no blood coming out," said Ogburn. "The aunt was giving him CPR and the man was pumping on his heart."

The boy was airlifted to the hospital, while his arm was taken by ambulance. En route, an Escambia County sheriff's escort that had been called in help speed the transport was involved in a car accident, Pensacola Beach volunteer firefighters said.

"It's our belief that (this) tragic incident has to do with visibility," Tomasovic said. "Sharks have very poor vision. When it's dark outside or the water is murky, if they see something splashing about they can't identify, they may strike."

Hospital officials said the doctors who worked to reattach the boy's arm might be available later in the day to discuss his condition.

"I think at this point I would just imagine he's going to be monitored very closely," said Pam Bilbrey, a spokeswoman for Baptist Hospital Pensacola.

The International Shark Attack File lists 79 confirmed shark attacks, 10 of them fatal, worldwide last year. That was the highest yearly total in the four decades since unprovoked shark encounters have been recorded.

Thirty-four of those attacks, nearly half, took place in Florida.

The shark attack also comes at the worst time of year for encounters between sharks and swimmers, according to Bob Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota.

The Fourth of July weekend, he said, typically is one of the worst weeks for shark encounters for the Gulf Coast and Southeast Florida, in part because sharks are hunting for fish along their migratory routes.

"It's sort of the whole peak season for the sharks, and it's the height of the beach season," he said. "This is a time when some of the larger sharks are not far from shore."