A hitman accused of murdering a notorious crime boss dubbed “Mr. Big” in 2015 and his associate three years later was sentenced to life in prison after police were able to pinpoint his movements with his GPS-enabled running watch.

Mark Fellows, 38, also known as “The Iceman,” shot Paul Massey, who was nicknamed “Mr. Big,” and his associate John Kinsella as part of a feud between rival gangs in Salford, United Kingdom, the BBC reported.

Massey, 55, a father-of-five, was shot and killed outside his Salford residence in July 2015. The jury at Liverpool Crown Court heard Massey was shot at 18 times as he tried to take cover.

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Three years later, Kinsella, 53, Massey’s "mob fixer" associate, was walking his dogs with his pregnant partner, Wendy Owen, at a path near their home in Rainhill, Merseyside, when Fellows gunned him down. He shot Kinsella twice in the back and once the back of the head.

Detectives were able to get key evidence from Fellows, a cyclist and runner, after seizing his Garmin Forerunner watch and tracking the GPS locations, the BBC reported. Following a raid of Fellows' apartment, police discovered the watch and were able to track the data that showed him at the scene where Massey was killed, The Washington Post reported. The media outlet reported a picture of him wearing the device at the Great Manchester Run in 2015 "put the item in his possession at the time of his killing."

Fellows was “convicted of both murders Wednesday but found not guilty of attempted murder of Owen,” The Guardian reported. He was sentenced on Thursday.

Before Fellows was led away, he yelled, “I didn’t shoot at Wendy Owen. She’s lying.”

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Steven Boyle, 36, who was is considered Fellows’ “brother in arms” and accused of acting as a lookout in Kinsella’s murder was found guilty of murder. He was given a life sentence of which he would have to serve a minimum of 33 years. He was cleared of Massey’s murder and the attempted murder of Owen.

Despite his nickname of “Mr. Big,” Massey stood at an average height of 5 feet, 8 inches, and was known in Greater Manchester for selling drugs during the 1990s.