Mark Callahan, 60, father, retired firefighter, and 'everyone's best friend'

The second-oldest of 10 children, Mr. Callahan had an expansive labor pool in his family and more potential helpers in a circle of friends that extended beyond blood ties. With his sense of humor and generosity, his family said, he reached out to all.

“If anybody needed some money, my father would put you to work for the day, even if he didn’t need you,’’ said his son Mark Jr. of Milton.

Mr. Callahan, who suffered a heart attack a few years ago, died in his sleep Thursday at his vacation home in Harwich, a placid retreat from the hustle and bustle of his Milton residence. He was 60, and his family is awaiting tests to determine the cause of death.

“He was an excellent builder, as well as being devoted to the Fire Department,’’ said his sister, Stephanie Campbell of Quincy. “He loved his job; he loved being able to help people. He did not mind going to work every day. If he was able to help people, he was happy to do that.’’

Helping was something Mr. Callahan did in both jobs, but he was not the kind of public servant who flaunted his sometimes dangerous work.

“We weren’t allowed to have a scanner,’’ said his son, a truck driver for the Globe.

He added that while his father loved working as a firefighter and arson investigator, department memorabilia did not play a dominant role in home decor. Details about work generally were not part of family discussions, either, unless someone inquired.

“ ‘Information in, not out,’ that was his motto,’’ his son said. “Tell people very little, take everything in, keep your cards close, you know what I mean? If you wanted to know something, he’d tell you. He’d come home smelling like smoke sometimes, and we’d ask him and he’d tell us. But he didn’t come home saying, ‘We had this big fire.’ ’’

Instead, “every opportunity he had to crack a joke, he would,’’ said Mr. Callahan’s other son, Brendan of San Francisco. “He was everyone’s best friend. He was a great inspiration.’’

Mr. Callahan, he said, “always put anyone at ease, especially the first time you’d meet him. I remember bringing my wife to meet my parents for the first time. When she left, she was like, ‘That was the easiest thing I’ve ever done.’ My dad wanted to know everything about her and just opened up himself, too.’’

Mark G. Callahan was born in Boston and grew up in Dorchester, the son of a firefighter. He graduated from Boston Technical High School in 1967 and two years later married Mary Ellen White, whom he had met on a blind date.

After Mr. Callahan’s mother died in the early 1970s, he moved back to his parents’ home, with his wife, to help his father raise his younger siblings, said his sister, a listings editor at boston.com.

“He was a rock for my family and for his own family,’’ she said. “He was an amazing brother, an amazing husband who just never complained about anything. Mark was a hard worker. He worked two jobs most of his life and was just beginning to enjoy retirement.’’

Mr. Callahan joined the Boston Fire Department in 1975 and spent 20 years as a firefighter at the Meetinghouse Hill station in Dorchester. Then he became an investigator for the arson squad, working a dozen more years before retiring.

He and his wife moved to Milton, where they raised two sons and two daughters, and he attended their hockey games, softball games, and track meets.

“He did everything with us,’’ Mark said. “Each one of us was different, and he found something to do with every single one of us.’’

“He was never one to tell us what to do; he was one to support what we wanted to,’’ Brendan said. “He set good examples for us. He taught us how to act respectfully, always work hard, and follow your dreams, that we can accomplish anything we want to as long as we put the work into it.’’

Mr. Callahan often conveyed such lessons with the good humor for which he was well known. His sister said that nearly everyone who passed through the receiving line at Sunday’s calling hours mentioned the way he would ease tension with the right joke, or simply bring smiles to faces with nicknames he coined or quick-witted observations.

Cape Cod was where Mr. Callahan retreated to leave firefighting and construction behind. Years ago, he and his wife bought the house in Harwich, intending to retire on the Cape someday. Fishing and boating were constants during the weeks he could spare away from home, but surrounding himself with family and friends was just as important.

“For him, the Cape was complete relaxation,’’ Brendan said. “My dad loved the beach. He was one of those guys who wanted to get there as early as possible and stay as late as possible, burying his feet in the sand and enjoying the sun as long as he can. He loved soaking up the sun and having people around him.’’

In addition to his wife, two sons, and sister, Mr. Callahan leaves two daughters, Amy Murray of Duxbury and Sarah of Milton; four brothers, Dennis of Hingham, Timothy of Weymouth, John of Braintree, and Jeffrey of Milton; three other sisters, Maryanne Walker and Patricia DeLuca, both of Weymouth, and Judith of Quincy; and four grandchildren.

A funeral Mass will be said at 10:30 a.m. today in St. Agatha Church in Milton. Burial will be in Cedar Grove Cemetery in Dorchester.