Conor McGregor's ex-coach, pro MMA fighter Jonathan Dargan, kills retiree in Dublin street fight

Just over a year ago, professional mixed martial arts (MMA) fighter Jonathan Dargan was using his proficiency in Taekwondo to help Ultimate Fighting Championship (UFC) featherweight phenom Conor McGregor prepare for Dennis Siver in Boston.

"It's great having Johnny around," SBG Ireland head coach John Kavanagh said prior to UFC Fight Night 59. "He's a hero to all the guys. I have never seen anyone that can move as fast as Johnny Dargan. He's got some freak genetics. I'd love for a scientist to measure his output, because it's absolutely bizarre what that man can do."

Those genetics weren't enough to garner him a winning record inside the cage, as "The Dragon" (1-3) was knocked out by Lukasz Parobiec at BAMMA 22 back in September, his second consecutive loss after Karl Roche submitted him at BFC 13 earlier in the year.

As far as his vaunted speed, well, that may have been instrumental in the death of 57-year-old Paddy Mullally, who was killed after getting slugged by Dargan in the streets of Dublin back on March 5. Mullally, who stopped to help settle a dispute between Dargan and his girlfriend, fell backwards and hit his head after being struck.

He died the next day.

"I'm so sorry, it was an accident," Dargan said (via Independent.ie). "I'm devastated and heartbroken for that man and his family. All I can say is I'm crushed. If I could take back everything that happened that night I would, but all I can do is beg his family for their forgiveness. It was a genuine mistake."

It was 3:30 a.m. and Dargan, 41, had been drinking since 8 p.m., according to the report, which led to the argument with his girlfriend.

The case has since been filed with the Director of Public Prosecutions.