A team of white horses carried Sgt. Sean T. Callahan’s flag-draped coffin on a caisson Monday as about 300 friends, family members and U.S. Marines followed to Section 60 in Arlington National Cemetery.

The Marine, who died April 23 in Afghanistan’s Helmand province, was buried with full military honors less than 24 hours after President Obama announced the death of Osama bin Laden.

Callahan, 23, was killed after the convoy vehicle he commanded rolled over a makeshift bomb, said his father, Patrick Callahan. Lance Cpl. Dominic J. Ciaramitaro, 19, of South Lyon, Mich., also died in the explosion.

Marine Cpl. Daniel Callahan, 26, saluted his little brother as a bugler played taps. Their older sisters, Heather, 34, and Melodie, 29, and mother, Janet, wept.

Being the youngest, Sean Callahan was always considered the favorite by his siblings, Patrick Callahan said. He had a tattoo of a heart with the word “Mom” on his arm that he would flash to win his mother’s favor, the elder Callahan said.

One of his sisters found temporary tattoos with the same design for the family to wear at the services.

Sean Callahan was born in Manassas but grew up in Gainesville. After he graduated from Brentsville District High School in 2005, his family moved to Warrenton.

Callahan’s friends described him as outgoing, full of life and a “Tasmanian devil” in dedications on Facebook and Legacy. He loved the beach, beer and music.

“Sean certainly wasn’t an innocent, but he had a smile that could turn any frown upside down,” his father said.

The guitar became Sean Callahan’s passion when he was in junior high, his father said. He studied with a jazz guitarist and played at family functions and with friends.

“He lived the life of a 60-year-old in 20 years,” Patrick Callahan said. “He packed it in.”

Patrick Callahan said he knew his son would join a police force or the military. He enlisted in the Marine Corps in March 2008.

“As hard as it is to fare this tragedy, he loved being a Marine. He loved having these guys around him,” Patrick Callahan said. “It was not a political situation. They have been given a mission. . . . In their hearts, their mission was to defend the freedoms that are so often forgotten.”

The mother of a fellow Marine in Sean Callahan’s unit e-mailed the Callahans. Patrick Callahan said the woman recalled that her son called Sean Callahan “a rare breed” and “a natural born leader.”

“Sean earned every award and every promotion without putting on a show to get it,” Patrick Callahan said, reading the e-mail out loud. “He was the real thing. [Her son] said he was the kind of Marine who never needed to demand respect. He got it naturally.”

Callahan was assigned to the 3rd Battalion, 9th Marine Regiment, 2nd Marine Division, II Marine Expeditionary Force based at Camp Lejeune, N.C. He was deployed to Afghanistan in December and served one tour in Iraq in 2009.

His awards include the National Defense Service Medal, Afghanistan Campaign Medal, Iraq Campaign Medal and Global War on Terrorism Service Medal.

Back at the cemetery, Daniel Callahan stood at attention to receive a flag in his brother’s honor. As the crowd left the grave site, Sgt. William J. Dixon, the Marine funeral director, gave Sean Callahan a final salute before leaving his white gloves on top of the coffin.

And Patrick Callahan thought about his family — and how it isn’t whole anymore.

“A guitar has six strings. There are six people in our family,” he said. “It is like someone came along and cut one of those strings. Something is missing.”