A former intern for Connecticut Rep. Jim Himes was fatally stabbed on July Fourth in Washington, D.C., during a robbery inside a crowded subway car.

The Metropolitan Police Department said Monday that detectives have made an arrest in connection with the death of the former intern, Kevin Sutherland.

They have identified the suspect as 18-year-old District resident Jasper Spires, who has been charged with first-degree murder while armed.

Sutherland, 24, worked in Connecticut on Himes’ 2010 re-election campaign, then as an intern in 2012 in the congressman’s Capitol Hill office.

“This is a terrible tragedy,” Himes, a Democrat, said in statement to FoxNews.com. “Kevin was a fantastic intern, dedicated staffer and loyal friend who was loved deeply by those who knew him. My thoughts are with his family, and I hope they know they are surrounded by love and support.”

A Himes staffer said Sutherland remained close with members of the Washington office.

Police said the incident occurred at about 1 p.m. Saturday as the train approached the NoMa-Gallaudet stop, within blocks of Capitol Hill and Sutherland’s home, in the Northeast quadrant of the city.

They also said first-responders arrived to find Sutherland with multiple stab wounds and showing no signs of life.

Spires had been arrested two days earlier in connection with an attempted robbery, according to police and court records obtained by The Washington Post. But Spires was released Friday when the charge was amended to a misdemeanor and new charges of assault were added, according to the newspaper.

Police Chief Lanier is reportedly looking into what happened.

“We’re pretty distraught that he was released for a similar if not less deadly crime two days earlier,” Joe Sutherland, the victim’s uncle, told The Post. “It led to a direct line to my nephew’s death.”

Sutherland, a graduate of American University in the District, was working for the digital strategy firm New Blue Interactive at the time of his death.

"I am heartbroken as is the entire New Blue team to hear the news of Kevin’s passing,” company founder and President Taryn Rosenkranz said in a statement. “He was one of the brightest political digital strategists in the country, and Kevin always had a smile. His murder was a tragedy and senseless. … The entire New Blue team’s thoughts and prayers are with his entire family and friends during this difficult time.”