The 15-year-old Waterboro boy whose disappearance May 8 prompted a massive search died from drowning after hitting his head, the state Medical Examiner’s Office announced Tuesday.

A spokesman for the medical examiner said an autopsy done Monday revealed that the cause of Jaden Dremsa’s death was drowning with blunt force head trauma, and that his death was accidental.

A memorial service for Dremsa will be held May 31, his mother wrote on a Facebook page that was set up during the search.

“We will never know what happened on May 8th. But that is the date of his death,” Jennifer Howard posted on the Facebook page Help Find Jaden Dremsa. “I pray that he did not know pain and that he did not suffer.”

On Saturday, nine days after the teenager was last seen, his body was recovered from Lake Arrowhead in Limerick, not far from his home in the Twin Pines Trailer Park in North Waterboro.

It’s not clear how the Medical Examiner’s Office concluded his death was accidental.

The area where Dremsa was found has a grassy shore, though the current may have moved his body. Tree stumps are abundant in areas along the shore where clear-cutting was done before the Little Ossipee River was dammed to form Lake Arrowhead.

Mark Belserene, spokesman for the Medical Examiner’s Office, referred questions about the manner of Dremsa’s death to the Maine Warden Service, saying the doctor who did the autopsy was not working Tuesday.

Cpl. John MacDonald, spokesman for the warden service, referred questions to the York County Sheriff’s Office, saying that once a search is completed, the warden service is no longer in charge.

York County Chief Deputy William King said he had not reviewed the medical examiner’s report so he did not feel comfortable commenting on that aspect of the case.

Don Dremsa, Dremsa’s grandfather, said he and other family members were searching in woods in Limerick when they got the news that a body had been found.

“Those woods and that lake probably won’t ever seem the same,” Don Dremsa said. We’ll always think about that.”

He said Jaden’s parents were too overwhelmed to speak to reporters Tuesday.

The teenager, who had been diagnosed with Asperger’s syndrome, a mild form of autism, was last seen on the afternoon of May 8, when he told his family that he was leaving to go for a walk in the woods. He was later seen by a neighbor on the shore of the lake.

Nine days later, his body was found near the lake shore in Limerick by a husband and wife in their pontoon boat. The couple waved down a warden service airboat that was in the area for the search and directed wardens to the body, which was floating in a few feet of water.

The body was off an island a short distance from the lake’s western shore, where the boy lived, said Don Dremsa, who wonders whether Jaden might have crossed to the island and then gotten disoriented.

When Jaden left his house that afternoon, he said he was going to take a walk and climb a tree. That raises the possibility that he fell from a tree and hit his head.

“He’s out exploring and may have slipped on something, and it sounds like that’s probably what happened,” Don Dremsa said. “I know he liked to play on the rocks. … It was kind of damp that night, pretty easy to slip if you’re jumping on the rocks.”

Don Dremsa recalled that when Jaden was younger and they went raking blueberries in eastern Maine, Jaden went exploring on a big rock pile. His grandmother asked him what he was doing.

“He said ‘I’m planting memories,’ ” Don Dremsa recalled.

Jaden liked playing guitar with his brother, Dremsa said, and the two were taking lessons.

“They were like twins,” he said. “His brother was two years older, kind of his caretaker. You didn’t see one without the other.”

A memorial will be held at 4 p.m. May 31 at Lakeside Community Church, which provided headquarters for the search. On several days, more than 100 volunteers were involved, as well as several state agencies and church volunteers who served donated food and drinks. The church even moved its Sunday services on May 11 so it wouldn’t disrupt the search.

“I truly believe that Jaden had a hand in bringing this community together somehow. In his kind and quiet way,” his mother wrote on Facebook. “Thank you again for all the kind words and prayers, and thank you for sharing your memories of Jaden.”

David Hench can be contacted at 791-6327 or at: [email protected]Twitter: @Mainehenchman