When His Best Friend Died on 9/11, He Became Like a Father to His 6 Kids - See His Early Father's Day Surprise (VIDEO)

(Screenshot: ABC News)

Lt. Larry Mack and Lt. Vinnie Halloran grew up together and became firefighters in the New York Fire Department together. When Halloran died on Sept. 11, Mack stepped in to be a father to his best friend's six children.

Mack involved the Halloran children in the life of his own family – he has a son and daughter – and created an extended family out of tragedy.

"Good Morning America" learned of Mack's story and surprised him on-air with a tailgate party with his family and favorite football team, the New York Jets. See the moving tribute video and celebration.