O'Connell football coach Steve Trimble runs his players through a practice in 2008. Trimble, 53, was found dead in his office at the Arlington school on Monday morning. (Kevin Clark/The Washington Post)

Steve Trimble, the football coach at O’Connell High since 2003, died Monday morning in his office at the Arlington private school. He was 53.

O’Connell Athletic Director Joe Wootten said he was told that Trimble had been running on the school’s track on Monday morning and was later found in his office around 11 a.m.

“I just couldn’t believe it,” Wootten said. “He was in great shape. He didn’t drink, didn’t smoke. He was a healthy guy.”

Trimble is survived by his wife, Gretchen, and four sons, who played on his football teams at O’Connell. Jeremy, Jordan and Justin went on to play football at Army, while Josh plans to play football as a freshman at Virginia Tech this fall.

Trimble graduated from Fort Hill High School in Cumberland, Md., and went on to play football at the University of Maryland. He played four seasons in the NFL – three with the Denver Broncos, one with the Chicago Bears — as a free safety.

Trimble began working at O’Connell in 1999 as a security officer and assistant football coach. He later became the Knights’ head coach and had a record of 30-51. He was named the Washington Catholic Athletic Conference coach of the year in 2008 after leading O’Connell to a 6-4 record. He recently was promoted to assistant dean of discipline at the school, Wootten said.

Wootten said it was unclear who will coach O’Connell’s team this season.

Funeral arrangements are pending.