A scuba-diving accident claimed the life of a Cudjoe Key teenager this week.

Kevin Piper Jr., 16, fell ill moments after surfacing from a June 26 dive to about 120 feet off Maryland Shoal, a Lower Keys reef, according to the Monroe County Sheriff's Office. He was flown by helicopter ambulance to Jackson Memorial Hospital in Miami, where he died Tuesday, according to accounts.

Initial reports indicate Piper may have run out of air and surfaced rapidly, putting him at risk of an air embolism. No cause of death had been released. Piper was diving off a 25-foot private boat with a group that included his father, Kevin Sr., and friends.

From witness accounts, Sheriff's Office Deputy Linda Kohout reported that Piper was diving by himself in about 120 feet of water. Zane Osborn, 17, was free-diving from the surface and watching Piper, who was making his second dive of the day.

"According to Osborn, Piper suddenly began to surface quickly," said agency spokeswoman Becky Herrin. "Osborn said he tried to tell Piper to slow down, but Piper motioned to him that he was out of air."

After surfacing, Piper said he felt "really weird," Osborn told Kohout.

Robert Pippin Jr., also on the boat, entered the water and helped Piper onto the vessel, but Piper fell unconscious. "Piper was breathing but would not respond to anyone," according to the Sheriff's Office.

The boat raced for shore to the Sugarloaf Marina, where a Monroe County Fire Rescue ambulance crew met it. Piper received treatment at Lower Keys Medical Center before being airlifted to Miami.

"Deputies took custody of Piper's gear at the scene," Herrin reported. "The gauge on his dive tanks showed it to be empty."

Divers memorialized piper as a fellow "Spearo" on SpearBoard, an Internet spearfishing forum. Piper is the seventh person to die in Florida Keys waters as an apparent result of a scuba or snorkeling accident so far in 2011.