The wanted man, Lee Aldhouse, is believed to be hiding in Phuket, an island in the south of Thailand heavy with tourism.
Longfellow was reportedly on vacation in Phuket, trying to learn the Thai martial arts form Muay Thai.
He and Aldhouse were involved in a bar room brawl, after Aldhouse allegedly attempted to stop Longfellew from getting to the restroom, according to CBS News.
Longfellow had punched the Briton and knocked him to the floor, before the fight broke up. Then he and his girlfriend left the bar, dropped her off at his rental home, and left to go to a 7-Eleven convenience store.
Aldhouse followed him and was intending to get even and went into the store after the former Marine left, stealing two knives.
Longfellow’s girlfriend, known as Oi, saw the kickboxer coming, according to the Phuket Gazette.
She said “at first it didn't look like he [Aldhouse] had anything. We didn't know he had a knife because his hands were in his pockets.” The men fought and Aldhouse pulled out his knife and stabbed Longfellow twice.
Oi said that they shut the door so Aldhouse wouldn’t get in, then called the police. Longfellow died before the ambulance came.
The police passed out pictures of Aldhouse, trying to find him.