A teenage boy was killed and two women badly injured off Waikiki yesterday when the mast on a commercial tour catamaran snapped, pinning the boy between the top deck and the cabin.

Witnesses said crew and passengers were unable to free him, but firefighters later were able to remove the mast by using airbags. The boy was airlifted to The Queen's Medical Center, where he was pronounced dead.

A 41-year-old woman also was airlifted to Queen's in critical condition.

The third victim, a 41-year-old woman, was brought to shore on the catamaran, Na Hoku II, which had to be towed by a U.S. Coast Guard boat. She was taken to Straub Clinic & Hospital in serious condition.

Police said the boy was from California but released no names.

Jamie Brandon of Winnipeg, Manitoba, was aboard the catamaran yesterday when the incident happened.

"Everything was going along smoothly; it was a fun time," Brandon said. "(Then) all of a sudden the mast snapped in one place, maybe two, close to the top and maybe about halfway up.

"Cables were flying all over the place and gashed one person on the head," he said.

Brandon said the catamaran cruise started at 3:30 p.m.

"Everyone was in quite a bit of shock," Brandon said.

The Coast Guard received the distress call from the 45-foot Na Hoku II at approximately 4:20 p.m. The boat, which was carrying about two dozen passengers, was about three-quarters of a mile off the Elks Club, said Honolulu Fire Department Capt. John Kino.

The Coast Guard sent its 47-foot motor launch and HH-65 Dolphin helicopter to the catamaran. Rescue personnel with the city's Ocean Safety Division arrived on the scene shortly thereafter.

According to emergency responders at the scene, the boy was unresponsive and pinned face-down. He was on the upper deck of the catamaran. The other two victims were on the lower deck.

The catamaran was towed to the Ala Wai Boat Harbor.

John Savio, owner of Na Hoku II, surveyed his catamaran as it bobbed in the water at the harbor dock and tried to make sense of what went wrong.

"I don't know what happened," said Savio. "The mast broke and pinned the kid, and we couldn't get it off of him. I don't know why it broke, either — whether it was a wire, or just metal fatigue, or what."

Wes Mundy, conservation enforcement officer with the Department of Land and Natural Resources, said a joint investigation was being conducted by the DLNR, the Fire Department and the Coast Guard.

"The passengers who were uninjured have been taken care of, and arrangements made to get them back to their hotels," Mundy said.

Sea and wind conditions may have been factors in the accident, said Bryan Cheplic, spokesman for the city's Emergency Services Department.

Northeast winds were in the 17-to-21-mph range yesterday afternoon.

"It was rough today," Cheplic said.

The boy and one woman were airlifted by helicopter to Kapi'olani Park, where ambulances were waiting to take them to Queen's.

Crowds of people flocked to Kapi'olani Park and the Waikiki natatorium to watch the rescue. Some snapped photos as helicopters flew overhead.

Coast Guard spokesman Petty Officer Michael De Nyse said he wasn't sure what the safety requirements are on tour catamarans or if Na Hoku II was up to code.

According to its Web site, Na Hoku II sails five times daily from Waikiki past Diamond Head and back.

The catamaran ties up in front of the Sheraton Moana Surfrider.

Such accidents aren't common in Hawai'i.

In July 2005, city lifeguards rescued a 40-year-old man when the mast on his sailboat snapped and struck him. The boat was about a mile offshore from Diamond Head.

In March 2004, the 47-foot Paragon Sailing Charters catamaran capsized, stranding 10 people on board for three hours before being rescued by a fishing boat from O'ahu. One of the passengers suffered a broken collarbone and a slight concussion.

In March 2000, nine passengers on a whale-watching sail suffered minor injuries when the catamaran Ho'onanea flipped over about four miles west of Waimea Bay.

Reach Catherine E. Toth at ctoth@honoluluadvertiser.com and Will Hoover at whoover@honoluluadvertiser.com.