Mr. Gowan, 38, the school's head boys' basketball coach and an associate director of admissions, was found dead Monday morning in his room in the faculty quarters in Sheehan Hall, a residence hall on campus.
The coroners' office had not determined the cause of death by Monday afternoon, according to Lt. Larry Ash, New Milford police public information officer.
Criminal aspect was not indicated in the death, Lt. Ash said.
"Don embodied everything that Canterbury stands for," said Tom Sheehy, head of school. "He was much loved by the faculty and students in the short time he was here. Our thoughts and prayers are with his family."
A standing room only turnout attended a service in Mr. Gowan's memory Monday in early afternoon in the Chapel of Our Lady on the Canterbury campus, Mr. Sheehy said.
The chapel seats 300. The student population at Canterbury is 350.
Gowan had come to Canterbury in August 2010 as an associate director of admissions.
The younger Gowan attended Trinity College, graduating in 1995.
Mr. Gowan taught and coached at both Kent School and Marvelwood School, both in Kent, for four years before coming to Canterbury.
Previously, he had worked for 10 years in Manhattan in the investment banking industry, according to his profile on the Canterbury website.
"I think Don wanted to follow his father's path," said Dave Wilson, athletic director at Canterbury for 15 years. "His father was beloved at Kent School and Don had found his true passion when he left Wall Street and began working with and coaching young people."
Mr. Wilson credited Mr. Gowan with turning the basketball program around.
He said Mr. Gowan "got the whole thing. He asked the questions, `Is this student growing? Is he a better person for being involved in sports?'"
"He didn't judge success by just wins. He taught the kids to play with integrity, to honor the sport and to honor their opponents. I considered him both a friend and a colleague," Mr. Wilson added.
Carter Moots, 18, played on the varsity basketball team in his junior and, this, his senior year at Canterbury with Mr. Gowan as his coach.
His coach was also Carter's academic advisor at the school.
"We both got to Canterbury at the same time," Carter said. "When I first got to Canterbury, I struggled academically and he played a big role in helping me bring my grades up."
"He kept saying he wanted the (basketball) team to be an example for the other students on campus," he added.
Lon Moots, Carter's father, said his son had transferred to Canterbury from a public school and "had no idea about the academic rigor expected at a prep school."
"We had many meetings with Don in Carter's junior year and he helped Carter catch on to what he needed to do to succeed," Mr. Moots said. "This year has been a complete turnaround for Carter."
"He's meeting all his requirements," said the elder Moots, "(and) was one of the co-captains on the (basketball) team this year."
Coach Gowan's Saints finished with a 17-9 record this winter, tying the program record for most wins in a season. Canterbury qualified for the New England tournament for just the third time and, for the first time, hosted a tournament quarterfinal game.
Mr. Gowan was not married.
He is survived by his mother GeorgeAnn Gowan, of Kent, and two siblings, Anna and Andrew Gowan.
A memorial service was held Monday, May 14 at Kent School.
Canterbury School is tentatively slated to hold a memorial service Sunday, May 20.
"Don embodied everything that Canterbury stands for... he was much loved by the faculty and students in the short time he was here. Our thoughts and prayers are with his family."
Canterbury School Head of School