Cayman Naib, the 13-year-old Newtown Square boy whose body was found Sunday, died from a self-inflicted gunshot wound to the head, police said Monday.

He likely died before his parents concluded he was missing and commissioned an intensive four-day search - involving hundreds of volunteers - that ended on the outer edges of the family's property, police said. He used a gun that had been legally purchased and owned by his father, Farid, said Newtown Township Police Chief Chris Lunn.

"The trigger lock that was on the gun didn't prevent the gun from being fired," Lunn said.

The gun was more than 30 years old and the trigger lock was not an adequate fit, said Delaware County District Attorney Jack Whelan.

The details of the death, which came after a medical examiner's review, answered questions that had lingered since the teen's disappearance Wednesday evening right before the season's biggest snowstorm.

Naib left home around 6:30 after receiving an e-mail from the Shipley School about overdue homework, his parents said.

He had left behind his cellphone, wallet, and glasses.

By Friday, family and friends had mounted an extensive campaign to find the missing eighth grader. They enlisted the help of hundreds of community volunteers to go door to door, walk roadsides, and comb through fields. Their movements were tracked with a GPS app and mapping program, and aircraft became involved in the search. The teen's computer and cellphone were taken to the FBI to be examined for clues.

On Sunday, a search dog found the boy's snow-covered body at the edge of the family's 13-acre estate, in a shallow creek bed covered with snow.

A "Find Cayman" Facebook page set up by the family had more than 21,000 "likes" before it was changed to "Celebrating Cayman." After the news of his death spread, family supporters began placing royal-blue ribbons on their mailboxes or trees to express their sympathies.

Whelan said the District Attorney's Office had reached out to the Newtown Township Police Department on Friday to help interview family, classmates, and friends of Cayman.

"In this particular case, there was no obvious evidence that he was suffering from depression," Whelan said. "There were no warning signs that this was about to happen."

"No words can adequately express the Naib family's pain and sadness at this news," said a statement on the Facebook page. "The family has asked that the community respect their need for privacy at this very difficult time as they mourn the loss of their son and support their daughter."

The statement said the family is still deciding how to celebrate their son's life and will announce the arrangements when they have been made.

"We were told that he did not suffer," the statement said.

610-313-8111 @MariSchaefer