A 21-year-old man killed Saturday while cutting branches from a tree in Fairburn died of asphyxiation.

Tim June of Roswell died of “head and neck compression,” said Sgt. Anthony Bazydlo, a spokesman for the Fairburn Police Department. The Fulton County Medical Examiner’s Office determined the cause of death Sunday, he said.

The accident occurred about 12:30 p.m. June was about 60 feet off the ground, working on a pine tree, when a branch struck him, Bazydlo said. The Fairburn Fire Department dispatched a ladder truck to the site, where firefighters worked carefully to extricate June and lower him to a waiting ambulance.

“It took some doing to bring him down,” said Bazydlo, who watched.

June’s death, said Bazydlo, confused and distressed police. At first, he said, they thought June had died from the force of the limb striking him. A physician determined otherwise.

“This,” he said, “is the definition of a tragic accident.”

June was the owner of Atlanta Tree Assurance, founded last year. Its Facebook page offers a brief but optimistic history of June’s company. It had just gotten business cards; T-shirts were on the way. One Facebook photo depicts two smiling young men wielding chainsaws. Another shows a man in a safety harness, wearing a hard hat, dangling from the leafy heights.

June had been cutting trees for three years and recently decided to start his own company, said his girlfriend, Sarah Docekal. He was an accomplished arborist, she said, at home in trees.

Docekal said she is nine months pregnant.

“We were going to give it up for adoption,” said Docekal, also 21. “Now, I may change my mind.”

June showed an independent streak from an early age, said his mother, Susan Coker of Marietta. She recalled watching him tear about the family’s 3-acre homesite on a dirt bike when he was 5. By the time he was 14, he was cutting grass and cleaning gutters for cash. Then he discovered tree cutting.

“He finally decided he could make more money as the boss instead of working for the boss,” his mother said.

In his spare time, Coker said, June liked to head to the hills, driving a customized Jeep pickup that he used for mud-bogging.

Sunday night, as she prepared to bury her son, Coker remembered the boy who became a man.

‘My son had the most charming smile,” she said. “He really loved his mama, and I really loved him.”