SEAFORD, NY (CBSNewYork) — Mourners lined the streets of Seaford Friday to remember John Capano, a federal agent who was killed in a “friendly fire” shooting while trying to stop a robbery on Long Island New Year’s Eve.

LISTEN: WCBS 880’s Sophia Hall reports

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Thousands of law enforcement officials from around the country gathered at St. William the Abbott Church in Seaford for ATF agent Capano’s funeral.

Attorney General Eric Holder spoke at the service, calling Capano “a true patriot” who had “extraordinary courage.”

“We’re supposed to be tough, but there’s a lot of tears shed,” ATF special agent Mike Campbell told CBS 2’s Jessica Schneider.

“John Capano is a hero,” said ATF special agent Steve Bartholomew. “He’s a patriot and he should be remembered as such.”

As an ATF agent, Capano traveled the world investigating bombings. But his final courageous act happened at home on Dec. 31.

He was at a pharmacy to pick up a prescription for his cancer-stricken father when officials say career criminal James McGoey, holding a pellet gun that looked like a .45 caliber handgun, tried to steal cash and hundreds of painkillers.

Friends and colleagues tell CBS 2’s Jennifer McLogan that Capano’s heroic actions New Year’s Eve spoke volumes to his character.

“He made the ultimate sacrifice to protect the public. He is a true hero,” said Bartholomew.

“John did what most trained law enforcement officers would do. He did what he thought was best in protecting the public from violent criminals,” said ATF special agent Gerry O’Sullivan.

John Capano's wife, Dori, and dad James (credit: Mona Rivera/1010 WINS)

Agent Capano chased the suspect, shooting him in the leg.

A few doors down, deli owner and  retired police lieutenant Christopher Geraghty and one of his customers, an off-duty NYPD officer, ran over to help but instead caused a tragedy amid the confusion.

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Officials say Geraghty killed Capano in what they’re calling a “friendly fire” shooting, something not lost on those in attendance.

“He thought he shot the perpetrator of the thing. It happened quickly, within five to ten seconds,” said Brian J. Davis, Geraghty’s defense attorney. “He didn’t have to learn that it was his bullet. My client knew. His life will never be the same.”

Capano’s brother James said the pain those families are also enduring must not be dismissed.

“However this turns out, I ask we that we pray for them too,” he said.

Funeral for ATF agent John Capano on Long Island, Jan. 6, 2012 (credit: Sophia Hall/WCBS 880)

“John was a very special special agent,” said Eric Immesberger, head of Long Island’s ATF Office.

“There’s been a lot of tears shed this week,” said ATF special agent Michael Campbell.

Geraghty’s son Ryan was at work at the deli on Thursday and described his father as a physical and emotional wreck. Geraghty has left town, unable to work.

“Yelling we’re police, we’re police,” said Davis. “Does he even hear my client shouting ‘who’s the good guy? Who’s the good guy?’  when you’re in a life and death struggle over a weapon?”

Once Geraghty realized Capano was the good guy, he tried desperately to save his life but it was too late.

Agent O’Sullivan was especially close to Capano. The two have been friends for 15 years.

“I’m still in shock,” he said. “I’m still trying to figure all this out.”

Capano is the first ATF agent to be killed in the line of duty by gunfire since 1993.

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