Gunnery Sargent Thomas J Sullivan was one of four Marines killed at the hands of Muhammad Youssef Abdulazeez in Chattanooga, Tennessee, on July 16.The murderer was shot and killed by Chattanooga police close to the scene of the killings.

Irish American Marine Sullivan, was 40-years-old and hailed from Springfield, Massachusetts one of the most Irish towns in America.. He had survived two tours of duty in Iraq and earned a Purple Heart. He grew up with two siblings, Joe and Denis, along with his parents, Jerry and Betty Sullivan, and went to Cathedral High School before going on to serve his country.

He was a huge fan of Boston Irish punk band The Dropkick Murphys, who, mourned his loss on Twitter. 

— Dropkick Murphys (@DropkickMurphys) July 17, 2015

He joined the US Marine Corps in September 1997 and studied criminal justice at American Military University.

A Facebook profile for the India Battery, 3rd Battalion, 12th Marines lists Sullivan as "one of our own."

His friend Josh Parnell, of Chicago, told the Oak Lawn Patch said "There’s no Marine you would want that was better in combat than him.

"He’d been shot at so many times over the years and then for this to happen at home in the United States."

#ChattanoogaShooting #Chattanooga R.I.P. GySgt Thomas Sullivan pic.twitter.com/Dlqrq8Cixj

— Humoritarian (@Humoritarian) July 17, 2015
His brother’s bar, Nathan Bill’s Restaurant and Bar in Springfield outside which American and Irish flags fly,  posted the following on its Facebook page:

“Rest In Peace Gunnery SGT. Thomas Sullivan. Anyone who went to Holy Cross School, Cathedral High School or grew up in the East Forest Park knew who Tommy was. He was our hero and he will never be forgotten. Please keep his family & friends in your thoughts & prayers. Thank you Tommy for protecting us.”

And the messages of grief poured in on the Marines Facebook page:

“I am proud to say I served with this Marine. RIP Brother and Semper Fi,” posted Chris Craig.

“God bless Gunny Sullivan’s family and friends. My husband served with him very recently before his separation in January… I met him and he was a great man….Rest in Peace, Gunny…,” wrote Sudan L. Reott.

Just days ago Sullivan was out jogging along Mill Road in Hampden, Massachusetts. Now his family are coming to terms with his death.

The family gathered at their Hampden home in an effort to make sense of the tragedy. The grieving Irish American family were bowled over by the sterile military document they received notifying them that their son was killed.

RIP Marine Thomas Sullivan, one of the victims of the #ChattanoogaShooting pic.twitter.com/e3DPsZkdvs

— Jake Tapper (@jaketapper) July 17, 2015

Congressman Richard E. Neal, head of the Friends of Ireland caucus, issued a statement on Sullivan's tragic death. 

“It was with profound sadness that I learned that Sgt. Thomas Sullivan was killed yesterday in a pointless act of violence at a military installation in Tennessee. He was a young man who served his country with honor and distinction and had his whole life ahead of him," Neal wrote.

"Raised in East Forest Park, and a graduate of Cathedral High School, Tommy Sullivan represented the best of what Springfield has to offer. He was a bright, courageous and charismatic individual who proudly wore the uniform of the Marine Corps to defend the country he loved. In so many, he was the personification the Marine Corps motto: “Always Faithful.” He was loyal to his family, friends and the extraordinary men and women in the armed forces he served with. We will all greatly miss this brave American hero.

 "During this time of sorrow, I want to extend my sincere condolences to the entire Sullivan family. It is hard to imagine the heartbreak and grief they are experiencing on the sudden loss of their son. Rest assured, they will remain in my thoughts and prayers.”

The gunman has been identified as Muhammad Youssef Abdulazeez (24). The FBI has not yet found any connections to international terrorism.

What we know about Muhammad Yousef Abdulazeez, gunman in #Chattanooga attack: http://t.co/3ydeFDl4xT pic.twitter.com/K64u6WeFK8

— CBS News (@CBSNews) July 17, 2015
Abdulazeez had recently traveled to the Middle East and FBI are investigating whether he acted alone.

US Attorney Bill Killian said there are no remaining safety concerns for the general public.

Tennessee Governor Bill Haslam acknowledged the "heroic action" taken against the shooter by the four Marines who died and others at the facilities

He said “Chattanooga is a great city with a broken heart.”

Tennessee Senator Bob Corker echoed Haslam's comments, saying the country is mourning the "senseless loss" of four heroes.

Gunnery Sergeant Thomas J Sullivan: Massachusetts family stunned by death of Purple Heart hero who survived two tours in Iraq.Twitter