METHUEN — Peter O’Sullivan was more than a teacher and a coach. He was a beloved man that his colleagues, students and athletes adored.

A Methuen resident, O’Sullivan, 56, was a staple at Central Catholic High School, where he taught math and coached cross country and track for the past 31 years.

He died unexpectedly on April 25 of an apparent heart attack while running in St. Mary Cemetery.

Central Catholic athletic director Peter Paladino said a man like “Coach O” is one of a kind.

“He was one of the good ones. He always had the best interest of the school and the students,” Paladino said. “He’s pretty close to irreplaceable. He truly was a spirit in the school.”

He is remembered as being more than a teacher and coach to many, including Angus MacDonald, a junior at Central who has been running for O’Sullivan since his freshman year.

“He was always there. You could tell him anything,” MacDonald said. “He would always give you advice. Not just on running but for life in general.”

Brian Ford and Chris Valence, who both graduated from Central last year and attend Bryant University together, also ran for O’Sullivan.

“I was a long-distance runner so he was a personal coach to me,” Ford said. “But he was so much more than just a track coach. He taught us so much more than just running. He was a very intelligent man. Over time he became like a second father to me.”

Ford added that O’Sullivan did not favor long distance runners over anyone else.

“He cared about the best runners as much as the average Joe just trying to get into shape,” Ford said.

Valence said O’Sullivan talked him into running and Valence was glad he did.

“I broke the 800 record for the school last year,” Valence said. “It was because of him. He always pushed me to be my best.”

That is something that O’Sullivan will be remembered for on the track and in the classroom — pushing his athletes and students to be the best they can.

“I remember the state championship last year. We got down early and ended up winning by a point,” Ford said. “It was him that picked us up. It wasn’t just the stars; he pushed everyone.”

Mike Leal, an assistant coach for 12 years, said although O’Sullivan held high standards on and off the track, he never took credit for the team’s success.

“When it came to praise and credit, he gave it all to the runners and the coaches,” Leal explained. “But we feel he, himself, has built the program to what it is today.”

Leal not only ran for O’Sullivan when he was a student at Central, he is also a teacher in the math department alongside Sully Grella, another assistant coach for the track team. Grella has served as assistant for the past 13 years.

Grella said O’Sullivan was the reason he returned to Central.

“It was because of him I came back as a teacher and coach,” Grella said. “I used to watch the way he lived his life in the classroom and on the track. He is such a huge influence, more importantly as a teacher than as a coach. He is a mentor as a teacher. It’s more about Pete the person.”

Although it will be hard, the team plans to continue its season as planned.

“It’s would be hard not to do it. It’s what he’d want us to do,” MacDonald said. “We have to keep going, do it for ‘Coach O.’ It will be hard, but it will be in his honor, the rest of this season.”

Leal said the assistant coaches will share the duties for the remainder of the season.

“We are going to finish the season the way he would have wanted,” Leal said. “I think the goal for the team is for the team to perform to the best of their ability. That was his plan every season.”

The team did decide not to attend the Class B State Relays at New Bedford Vocational School on April 29. Instead, the squad attended their coach’s funeral.

“As a coaching staff we decided to be there to support his family,” Leal said. “And the boys decided they also wanted to pay their respects.”

O’Sullivan’s records as coach of the cross-country, indoor and outdoor boys’ track teams speak for themselves, but Grella said his records are only the tip of who O’Sullivan was.

“Look at his stats, the titles he’s won; they’re outstanding,” Grella said. “But more so he was a decent all-around human being, not just a track coach, which was more important.”

O’Sullivan’s Red Raider teams have compiled 32 Merrimack Valley Conference championships — seven cross-country, 12 indoor track and 13 outdoor. They have won six relay championships and eight class championships.

“The whole MVC track world is grieving,” Paladino said. “It’s a terrible loss for the track world in the Valley and the state.”

In a written statement from Central Principal David M. DeFillippo, O’Sullivan’s career at Central is described to a tee.

“Peter O’Sullivan was a demanding teacher, who enabled his students to reach a level they never thought they could reach by providing them with the confidence and ability to succeed,” DeFillippo said. “He really loved children — his own children, his grandchildren, and the thousands of students whose lives he touched as a teacher and coach. The kids knew he cared; he would never let them settle for anything but the best for themselves.”

O’Sullivan is survived by his wife Deborah, his three daughters, Kendra and Tatum O’Sullivan and Rebecca (O’Sullivan) Merrill; son-in-law Christopher Merrill, a Central Catholic guidance counselor; and two grandchildren, Colby and Haley Merrill.