Dominic Peterson, a 19-year-old sophomore on the St. Mary's College rugby team, died Friday, Sept. 4, after collapsing during a training run in Moraga — the team's first practice of the season.

Peterson fell during the roughly two-mile run and was helped back to his feet, but he collapsed a second time near the pull-up bar area after the run, according to accounts from teammates reported by KTVU. Mario Storti, a former St. Mary's rugby captain who was helping with practice and riding a bike behind the team, called 911 and used his lifeguard training to begin CPR before paramedics arrived. Peterson was taken to a local hospital, where he died. No autopsy results were available as of Saturday.

The emergency happened on a public jogging path, according to the San Francisco Chronicle. Fire Chief Jeff Isaacs of the Moraga-Orinda Fire Protection District confirmed Saturday that the district responded but did not comment further.

Peterson was a decorated player. The son of a rugby coach, he had co-captained a squad that won the national All-Star Tournament three consecutive years. He was also selected for the national Under-19 team that won the Rugby Americas North Championship.

"He had all the hallmarks of someone who would be progressing to play internationally at some point in his career," said Adriaan Ferris, director of California Grizzlies Rugby, who coached Peterson for years.

Ferris said Peterson was the kind of competitor who would help opposing players to their feet after tackles and compliment them on good plays. David Pool, head of USA Youth and High School Rugby, called Peterson a natural leader and described the loss as an indescribable tragedy.

The St. Mary's men's rugby team finished the 2025-26 season 13-2 and reached the CRAA National Semifinals, according to the college's club sports recap. Peterson played the same position as team captain Matthew Abbes, and the two worked closely together.

St. Mary's held a community mass for Peterson on Saturday, Sept. 5. O'Brien said the chapel was packed. "This is heartbreaking for our community and our deepest sympathies are with his family and loved ones. Dominic's smile was contagious and one that would brighten a room when he entered. He always gave 100% effort and encouraged those around him to do the same," the team wrote in a Facebook post. The men's basketball team also posted a dedication, calling the loss unimaginable.

St. Mary's College President Roger J. Thompson released a statement calling Peterson's death "a heartbreaking loss for our entire community," adding: "Our deepest sympathies are with his family and loved ones, and with the teammates, coaches, classmates, faculty, and staff whose lives he touched. We hold all of them close in our hearts and prayers as they confront this unimaginable loss."

Peterson's family said they are still awaiting answers. "At this point, we don't actually know the technical component of his passing, so that's something we have great interest in because he was such a fit kid," his father, Robert Peterson, told CBS News. "He was amongst the fittest on a very fit team." The family said Peterson's cause of death is still being determined by the medical examiner.

Peterson's family established the Dominic Peterson Memorial Fund to support men's rugby at St. Mary's, according to the Mercury News.

Teammates are expected to return to practice Tuesday for the first time since Peterson's death.