Jeff Haynes/Associated Press

The Minnesota Vikings announced that offensive line coach Tony Sparano died unexpectedly early Sunday morning. He was 56.

The team's owners, Mark and Zygi Wilf, released the following statement:

“Our hearts go out to Jeanette and the entire Sparano family as we all mourn the loss of Tony. Tony was a passionate and driven individual who cared deeply about his family, and especially enjoyed spending time with his grandchildren. Tony's presence within the Vikings organization will be deeply missed. We are only thinking of Tony’s family during this incredibly difficult time. We ask that the entire NFL and Vikings family keep the Sparanos in their thoughts."

Chris Mortensen of ESPN (via Adam Schefter) reported that Sparano "complained about chest pains" and went to the hospital Thursday but was released Friday after testing.

Mortensen (via Schefter) added Sparano was about to leave for church when he was found unconscious and could not be revived.

A number of NFL players also expressed their condolences:

A cause of death remains unknown.

Sparano began his NFL coaching career in 1999 with the Cleveland Browns as a quality control coach and offensive line coach before stints as a tight ends coach for Washington (2001) and the Jacksonville Jaguars (2002). He then spent five seasons with the Dallas Cowboys, serving multiple roles, before the Miami Dolphins hired him as a head coach in 2008.

Sparano spent four seasons as Miami's head coach, going 29-32 and leading the team to a playoff appearance. His time in Miami is perhaps most famous for the wildcat formation that Miami utilized to catch teams off guard, with running backs taking a direct snap from center, starting a fad around the league.

In 2012, he served as the offensive coordinator for the New York Jets before spending two seasons with the Oakland Raiders, which included a 12-game stint as the team's interim coach in 2014.

From there, he returned to his roots as a tight ends coach in San Francisco for a season before being hired by Minnesota to coach the offensive line in 2016.