A friendly Saturday night of drinking at a Panama City, Fla., nightclub ended with the seemingly unprovoked, fatal beating of a Canadian airman in front of his girlfriend and a roommate.

Master Cpl. Martin Brayman, 33, a 13-year-veteran of the air force, died of his injuries in hospital almost two days after the encounter, a spokeswoman for the Bay County Sheriff's Office said Wednesday.

Ruth Corley said a Tallahassee, Fla., man, Justin Timmons, 23, was arrested Monday and charged with what's known under U.S. law as an open count of murder. A more specific homicide charge is expected to follow once prosecutors examine the evidence gathered by the sherrif`s office.

Brayman was "sucker-punched" and violently beaten and the motive for the attack is unclear, Corley said in an interview with CBC News.

"Brayman never saw it coming," she said.

Early Saturday evening, the victim, who was assigned to the nearby Tyndall Air Force Base in northwestern Florida, had been in a nightclub when he met four men from outside of Panama City who had driven to the tourist hot spot to celebrate a birthday.

Brayman invited them to his home, where his waiting girlfriend and roommate were both uncomfortable with the strangers. According to the sherriff`s office, Brayman apologized and asked the four to leave, offering to meet them later.

Once in their car, the men realized they didn't have the airman`s contact details. They returned to the home and Brayman went outside to meet them while his girlfriend and roommate watched.

As the Canadian exchanged numbers with the driver, a man waiting in the car apparently grew agitated, jumped out and punched Brayman in the head, said Corely.

"Other people in the car were quite shocked when he got out and hit him," she said "They had no idea it was coming."

Brayman fell to the ground and was struck repeatedly, after which the men left.

An autopsy is to be conducted, Corley said.

The Department of National Defence said Brayman, a Norad air controller, was a veteran of two overseas deployments prior to being posted to the U.S.

There are more than 300 members of the Canadian military stationed in the U.S. on various duties.

The Canadian military said Brayman's next-of-kin have been notified and are being offered support.

Brayman is the second member of the Canadian military to die on assignment outside of the country this year.

Bombardier Patrick Labrie, a member of the 2nd Regiment, Royal Canadian Horse Artillery based at Petawawa, Ont., died in a parachuting accident in Bulgaria in June.