Mike Guglielmo has been in a lot of fights in his life, but none of them compares to the one he's in now.

Driven by the sickness and eventual death of his young son Giovanni, the Belmont ex-con has made it his mission to battle cancer, and for more than five years this most unlikely angel of mercy has been working hard in his crusade.

Friday night, his fighting past and present merge in a sense, as Guglielmo's “Fight Blood Cancer — Do It for Giovanni” bone-marrow drive coincides with the Combat Zone 42 mixed martial arts event at Rockingham Park in Salem.

Erik Tseronis, a local MMA fighter and registered bone-marrow donor, has a bout in the event, which also features undefeated Jimmy Quinlan, a Moultonborough police officer and world Brazilian Ju-Jitsu champion.

Guglielmo, who once organized a local underground fight club and later spent almost 18 years in prison after firing a machine gun at Manchester police officers in a 1985 standoff, today is now one of the top individual recruiters of bone marrow donors in the country.

Dale Robinson was the tactical commander of the SWAT team in the 1985 standoff. That night, he gave his officers the green light to shoot Guglielmo. (Amazingly, no one involved in the incident was injured.) Today, Robinson speaks with Guglielmo on a regular basis and has even helped him organize a bone-marrow drive.

“I think he is very much a changed person,” Robinson said. “I think he's really focused now.”

“It's redemption. It's really redemption,” Guglielmo said. “That's a rare thing.”

Redemption began in prison, where Guglielmo earned his his high school, paralegal, college and master's degrees. His ongoing mission began when Giovanni was diagnosed with a rare blood disease as an infant in 2006.

Guglielmo's desperate efforts to help his son led him to the marrow-donation organization DKMS Americas, and he made a pledge.

“I said, 'What are the chances (Giovanni will beat the blood disease)?' and (DKMS representatives) said, 'One in 20,000,'” Guglielmo recalled. “I said, 'No problem; I'll put 20,000 on the registry,' and they looked at me like I was crazy.”

He has been better than his word. To date, Guglielmo has registered more than 50,000 potential donors and found 150 matches, all of whom potentially could save someone's life. It's been an effort of international impact, including in Italy, which, inspired by Giovanni, earlier this year conducted its first national bone-marrow drive.

Ultimately, though, Guglielmo couldn't save his son, who beat the blood disease but died in April from gastrointestinal complications. Devastated by Giovanni's passing, Mike resolved to honor the boy's legacy by carrying on the fight against blood cancer.

“This is pretty impressive,” said Annette von der Muehlen, the head of donor recruitment for DKMS. “He has the passion, and he gets people on board.”

“It's an honor (that) because of my son all these other people got to live,” Guglielmo said. “It allows you to believe that there was a larger reason for him to be here.”

“Fight Blood Cancer — Do it for Giovanni” began last month with a series of marrow drives at local night clubs and culminates Friday night. But, Guglielmo said, his coordinated efforts with the MMA community won't end at Rockingham Park. He hopes to extend the partnership to other New Hampshire locations and eventually have it spread throughout New England and beyond.

The owner of Manchester-based Team Burgess, Nate Lamotte, was very close to Giovanni and had all of his fighters register with DKMS. Tseronis, one of those fighters, is determined to be a match.

“We're looking for 10,000 (donors) and beyond. That's just a number to start with,” Tseronis said of the MMA efforts. “With this cause, we're actually helping people get the chance to do something bigger than fighting.”