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Kathy Kmonicek, Associated Press
The casket of ATF Senior Special Agent John Capano is carried into St. William the Abbott Roman Catholic Churchfor his funeral on Friday, Jan. 6, 2012 in Seaford, N.Y. Capano, 51, was shot on Dec. 31, 2011 in Seaford, N.Y. while struggling with a suspect during a robbery for painkillers and cash at a pharmacy.

SEAFORD, N.Y. — Mourners lined the streets for the funeral of an ATF agent killed in a friendly fire shooting while trying to stop a robbery in a New York City suburb.

A silver hearse carried the body of agent John Capano to a church in Seaford, on Long Island.

Thousands of law enforcement officers stood at attention as it passed Friday. Pipers played "Amazing Grace."

Attorney General Eric Holder spoke at the service. He called Capano "a true patriot" who possessed "extraordinary courage."

Capano was killed Saturday while struggling with a robbery suspect. The fatal shot was fired by a retired police lieutenant who had also rushed to the scene alongside an off-duty police officer.

Capano's older brother, James, asked mourners to pray for them, too, saying they had also been trying to stop a crime.