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New York (CNN) Moments after American Airlines Flight 11 struck the World Trade Center North Tower on September 11, 2001, Officer Brian Cooney answered the call of duty.

Asleep at his mother's house on his day off with his Nokia flip phone by his side, Cooney was awakened by a phone call from his bosses at the New York Police Department requesting he respond to the disaster.

For the next six weeks, Cooney would come to work at Ground Zero every day -- the ashes still smoldering behind him as he struggled to breathe through a surgical mask with his Glock 19 sidearm strapped to his waist.

Now, 18 years later, Cooney has gone beyond the call of duty by donating one of his kidneys to a complete stranger.

Cooney didn't know his selfless act would set in motion a remarkable chain of kindness that would eventually save two lives, including that of a Major League Baseball all-star.

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Cooney, 45, of Oakdale, New York, is now a Port Authority Police Officer at LaGuardia Airport in Queens.

Along with his desire to help, he said his decision to donate a kidney was an attempt to repay his good fortune that he remained healthy after 9/11 while other first responders contracted deadly diseases and lost their lives.

"There's no real impetus, it's not like someone in particular was sick or any one story put anything in motion for me," Cooney told CNN on his final day on the job before surgery and six weeks of bed rest.

Of the list of responsibilities for the outgoing officer, Cooney is the de facto patrolman protecting and coordinating logistics for VIPs flying in and out of the airport.

'The best thing that could ever happen'

Assisting and hobnobbing over the years with big names like Muhammad Ali, the Rolling Stones, both Presidents Bush, and Donald Trump before he was President, Cooney even helps the New York Mets come through the airport (despite being a die hard Yankees fan).

Cooney feels a great pride in helping some of the more notable folks he encounters, keeping a readily accessible photo collection in his iPhone, as well as plastered on his police station locker.

But when he places his uniform back in that locker at the end of the day, the lifetime New Yorker takes home his kindness and sense of duty with him -- no matter who it's for.

"I've always been excited about helping people," Cooney told CNN. "Sometimes that's a simple task, like giving them directions or showing them around and helping them find their way. Once in a while you get a chance to do bigger things, but you never really know what's going to happen at work -- every day is different."

Not knowing who he would be giving his kidney to, Cooney put away his Glock last Tuesday at 5 a.m., before his mother drove him to surgery.

Three other strangers would also check into the hospital for simultaneous surgeries that day.

Hours later, Cooney's police officer kidney would become the kidney of a firefighter, saving the life of 55-year-old Al Barbieri, a 36-year volunteer firefighter with Long Island's Glenwood Landing Fire Department. Barbieri was diagnosed with kidney cancer in 2007, resulting in his kidney being removed.

"I was a young healthy guy, I was active duty and responding to calls. All of a sudden here I am, I'm the guy who's sick, and you're not used to being the guy that's always sick," the firefighter told CNN after his surgery.

"And when I found out that the guy who was donating to me was a police officer who was 45 years old, I couldn't have handpicked a better person to be a donor for me. That's like the best thing that could ever happen," Barbieri said.

Barbieri no longer needs the dialysis he's been dependent on for the past few years. He and his family would become ever grateful to his brother in blue. "Police officers are here in the world today so firemen can have heroes too," said Barbieri.

Thomas Buchta, the fire department's chaplain and Barbieri's lifetime friend, described the struggle to find a kidney for Barbieri, telling CNN "what's happened now is just an answer to prayer" that had gone unanswered far too long.

Grand slam of giving

The spirit of giving continued. Barbieri's wife Debbie Barbieri had offered her own kidney to her husband, but her blood type wasn't a match.

She decided to pay Cooney's gift forward by offering her kidney to someone else, as part of a "paired exchange."

So on Tuesday last week, on the same hospital floor as the two first responders, Debbie Barbieri's kidney was also removed and given to a different kind of hero.

Sports hero Ed Kranepool would be the final recipient of this grand slam of giving.

Port Authority Police Officer Brian Cooney, left, and New York Mets hall-of-famer Ed Kranepool.

Now 74, Kranepool played first base for the New York Mets in 1969, helping them to win the World Series and earn the nickname "The Miracle Mets."

"I've had two good teams in my life, the Mets and this team today," Kranepool said Friday after surgery.

"To Brian, Best Wishes. Ed Kranepool. 69 WS Champs. Thanks for saving my life!"

Kranepool would be next on Cooney's roster of celebrities he was excited to meet, despite Cooney's fierce allegiance to a nemesis team.

The introduction took place in wheelchairs after their successful surgeries.

Kranepool stood up out of his chair -- Debbie Barbieri's kidney now a part of him.

Posing with Kranepool, Cooney snapped yet another photo with a celebrity he was helping.

But Kranepool's gratitude didn't stop there.

Cooney received a gift that he said he'll be proud to show all the guys at work when he's back -- an autographed baseball from the Mets hall-of-famer.

The autograph reads: "To Brian, Best Wishes. Ed Kranepool. 69 WS Champs. Thanks for saving my life!"

It's a memento that will be added to Cooney's work locker, and as Cooney put it, it's "the best autograph ever."