The founder of the Twin Cities Running Club (TCRC) died unexpectedly Sunday, leaving a legacy as a quietly driven and supportive volunteer and coach in the Minnesota and broader running community.

David Coyne, 67, died Sunday afternoon at United Hospital, where he arrived by ambulance earlier in the day from his St. Paul home after calling a running friend for help. A few days before, Coyne said he had the flu, said Jim Richardson, also of St. Paul. Coyne had told his twin brother, Doug, the same thing Saturday.

Coyne's cause of death is undetermined.

News of his death was met with disbelief at its suddenness — and sadness at losing a person who has been part of the running scene for decades.

An attorney by trade, Coyne was a Twin Cities Marathon board member in the 1990s and created TCRC in 2003.

Richardson, club president and treasurer, said Monday that Coyne's absence leaves a profound hole in a club he loved — he'd send popular weekly newsletters about the group's twice-weekly runs, with bits of history, encouragement and more. The group has 150 members, about 30 of whom are regularly active.

"It is just a really wonderful group of people," said Richardson, who came on in 2010. "All due to Dave setting the tone."

Runner's World magazine named Coyne a "local hero" in 2011 for his commitment to people new to running. One of Coyne's motivations for starting the club was for runners who got into the sport through training on charity teams and needed guidance afterward to continue running. He'd been a coach for the Leukemia and Lymphoma Society Team in Training.

"Think of Coyne as the running version of Match.com, working to tailor the perfect training plan for every runner, no matter the background or goal," the magazine wrote.

Ryan Lamppa, then with USA Track and Field (USATF), crossed paths with Coyne in the early '90s. The two, along with several others in groups at the center of U.S. running, would found Running USA, an organization of races and industry stakeholders at the center of action.

"He was a bulldog about getting it founded and off the ground," Lamppa added.

Filled with emotion Monday night, Doug Coyne said road running and sharing it widely was the center of his brother's life.

"He just loved doing it. The community was a big thing," Doug Coyne said. "He said with the running club, he was very proud of the fact they welcome everybody, not just the fast people. Six-hour marathon — it didn't make any difference."