BANGKOK (AP) — Last month, an American man and his teenage son tragically lost their lives after being attacked by wasps during a ziplining experience at an adventure camp in Laos. The pair were stung multiple times, according to a hospital official on Thursday.

Dan Owen, who served as the director of an international school in nearby Vietnam, and his son Cooper, encountered the wasp swarm on October 15 at Green Jungle Park. The incident occurred as they were descending from a tree at the conclusion of the zip line.

This adventure camp is situated near Luang Prabang, a well-known tourist destination in Southeast Asia that has been recognized as a UNESCO World Heritage Site since 1995.

After the attack, both were initially treated at a local clinic before being transferred to Luang Prabang Provincial Hospital, where they arrived in a critical state, as explained by Jorvue Yianouchongteng, the emergency room physician on duty.

“The son was already unconscious and succumbed to his injuries within half an hour, while the father, though conscious upon arrival, passed away about three hours later,” he informed The Associated Press. “Despite our best efforts, we could not save them.”

The doctor said both had suffered from severe anaphylactic shock after being stung more than 100 times across their bodies, but that exact cause of death had not been determined.

The Asian giant hornet, known as the “murder hornet” due to its aggressive behavior toward other insects, is found in Laos but so are several other species of wasps. It was not clear which type had stung the two.

The local clinic where the two were first treated refused to comment and the Green Jungle Park did not respond to a query from the AP. The Laos Foreign Ministry also did not respond to a request for comment.

The U.S. State Department said it could confirm the deaths of two U.S. citizens in Luang Prabang but would not comment further “out of respect for the privacy of the family and loved ones.”

In a Facebook post, Owen’s employer, Quality Schools International, praised him as “touching countless lives” during 18 years with the chain, which operates 35 schools around the world. It said he had worked at five of its schools and was director of the QSI International School of Haiphong in Vietnam at the time of his death.

“He was deeply loved across our community and will be profoundly missed,” the school said. “Our sincere condolences go our to the Owen family and all who knew and loved them.”