One of the first men to ever step into the UFC Octagon died this week, according to multiple reports.

Kevin Rosier, who took part in the UFC 1 tournament in 1993, was ill for quite some time and suffered an apparent fatal heart attack Tuesday morning, UFC co-founder Art Davie confirmed with MMAFighting.com. Rosier was 53 years old.

Rosier won the second aired fight in UFC history, defeating Zane Frazier via TKO by way of head stomps on Nov. 12, 1993 in Denver, Colo. He went on to lose to Gerard Gordeau by TKO in the semifinals of the tournament. Before embarking on an MMA career, Rosier was a multiple-time kickboxing champion.

Rosier, an upstate New York native and Florida resident, also competed at UFC 4 in 1994, falling to Joe Charles. He lost twice in his MMA career to Dan Severn and had a 2-6 record when he retired in 2000.

Rosier most recently living in a retirement community in Tennessee, according to a 2013 story from Nashville Scene. He had open-heart surgery and fell while already in intensive care in recent years. Rosier spent most of the last decade in and out of VA hospitals.

"I'm lucky to be alive," Rosier told the magazine at the time.

Davie said Rosier always struggled with his weight and when he was booked for UFC 1 he was around 325 pounds -- about 80 pounds more than what he originally claimed. However, Rosier won an upset over Frazier in the quarterfinals of the tournament and it was one of the highlights of his career.

"He was the hailest and happiest guy at the [UFC 1 after] party," Davie said. "He was so proud that he had won that first bout."

Davie, whose 2014 book "Is this Legal?" chronicled UFC 1 and how the organization was built, said Rosier was incredibly confident heading into the first UFC, even when Davie caught him naked in bed with a woman a few days out.

"I asked him, 'Kevin, are you going to be f*cking ready?'" Davie said. "He says to me, 'Arturo, when I come in that right hand is going to settle this whole thing. I'm going to show you.' He was in indefatigable. You couldn't seem to put him down emotionally. He seemed to be very buoyant that week."

Davie painted Rosier as a ladies man, who stayed with an ex-wife in Colorado during part of fight week, but always had other girlfriends showing up. Rosier also had a root canal the week of the fight and was on a diet of white rice, hot sauce and Snickers bars washed down with Dr. Pepper, according to Davie.

But what Davie recalls most about Rosier was not his eccentricities, but his kindness and ability to get along with everyone.

"That's my memory of Kevin -- a big, lovable lug who had a heart as big as he was," Davie said.