Longtime quarterback coach and Tom Brady mentor Tom Martinez died Tuesday at the age of 66 after suffering a heart attack during a dialysis session, WCVB-TV Boston reported.
Tuesday also marked Martinez's birthday, according to NFL.com.
Martinez is considered one of the greatest coaches from the junior college ranks and is a member of the College of San Mateo's Hall of Fame. Complications from diabetes led to serious health issues late in his life and he had been in need of a kidney transplant.
Last month, Brady tried to help Martinez in his search for a new kidney by reaching out to his fans for help, myFOXboston.com reported.
"This is just oh, so terribly sad," Martinez's widow told the New York Daily News.
"He had so much to offer so many people."
The relationship between the two began in 1992, when Brady was in high school. Brady continued to consult Martinez for passing tips and advice throughout his college and NFL careers, with the two frequently working on mechanics during the offseason.
Martinez retired from coaching at California's College of San Mateo in 2005 because of his health problems but continued to work with quarterbacks at camps and on an individual basis.
Speaking with Sports Illustrated last year, Brady described Martinez as a "great man and coach," adding, "no one's helped me more as a passer."