Callahan enlisted in the active Marines after the attacks of September 11, 2001. ‘‘He had been in the Reserve, and he signed up because he felt this country was worth fighting for - and then he re-enlisted and went back to Iraq a second time,’’ Callahan volunteered for Toys For Tots in the South Shore area, and also enjoyed Harley-Davidson motorcycles, going to the beach and working in his yard and around his home. Family and friends described him as a devout Catholic who set up an informal ministry for other Marines, who shared their concerns and worries with him.

Callahan enlisted in the active Marines after the attacks of September 11, 2001. ‘‘He had been in the Reserve, and he signed up because he felt this country was worth fighting for - and then he re-enlisted and went back to Iraq a second time,’’ Callahan volunteered for Toys For Tots in the South Shore area, and also enjoyed Harley-Davidson motorcycles, going to the beach and working in his yard and around his home. Family and friends described him as a devout Catholic who set up an informal ministry for other Marines, who shared their concerns and worries with him.