A 15-year veteran of the New York Fire Department was one of three U.S. Marines killed Monday in an attack on a vehicle near a major American military base in Afghanistan, New York City Mayor Bill de Blasio's office confirmed Tuesday. Staff Sgt. Christopher Slutman, 43, is the fourth FDNY member to die while serving in Iraq and Afghanistan.

"They knocked. I went and turned the porch light on. I opened the door and saw the uniform. I said, 'This is not good,'" the fallen firefighter's father, Fletcher Slutman, told CBS New York.

U.S. officials said Slutman and two others were killed by a vehicle that had pulled over while a convoy of American military vehicles passed it. But when the military vehicles were next to it, the first vehicle exploded. The Taliban claimed responsibility for the attack.

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The U.S. and NATO Resolute Support mission said the American troops were killed near the Bagram Air Base, north of Kabul, while three others were wounded in the explosion. The base in Bagram district serves as the main U.S. air facility in the country.

Christopher Slutman NYC Mayor Bill de Blasio

A somber ceremony was held Tuesday near Slutman's firehouse, Ladder 27 in the Bronx, and members of Ladder 17, where he previously worked, also came to pay their respects. De Blasio led a moment of silence Tuesday morning as well.

"This, unquestionably, is an example of the measure of this man. Christopher Slutman, an American hero, a New York hero and we mourn his loss today," de Blasio said.

Slutman was awarded the Fire Chief Association Memorial Medal for saving a woman's life in a Bronx fire in 2013.

The FDNY traveled to Slutman's home in Delaware to help support his wife and three young children.

"It affects, I think, everybody, everybody once you lose somebody, especially when you kind of knew them, in your neighborhood. So yeah, it's very very saddening," neighbor Alex Montag told CBS New York.

"Together, all firefighters grieve the loss of our brother, Christopher, who dedicated his life to protecting the people of this city, and our nation," said Gerard Fitzgerald, president of the FDNY-UFA Firefighters Association.