WASHINGTON (DC News Now) — The Metro Transit Police Department (MTPD) said someone shot and killed a man who was on a Green Line train late Sunday morning.

Officers said that MTPD and Metropolitan Police Department (MPD) responded to the shooting at Navy Yard Station around 11:45 a.m.

When officers arrived at the scene, they found the man who had been shot. He died there.

An early investigation by MPD suggests that the suspect got on the Green Line Metro stop at L’Enfant Plaza and once on the train, he got into an argument with the victim.

The argument escalated while on the train and then the suspect shot the victim multiple times.

MPD said the suspect then got off the train at the Waterfront Station. The train continued until it stopped at the Navy Yard Station.

Passengers said Sunday night they’re not too worried about safety.

“Try to be extra cautious and vigilant. I think I feel most safe,” said Ivan Panado.

Others want to see added security measures, like the head of the D.C. Guardian Angels who said he would like to see metal detectors installed at train station entrances.

“It’s touchless so you don’t even know it’s really there,” said John Ayala. “You just walk through, and it will pick up on you, scan you really quickly, and see if you have any weapons.”

MPD said they have a person of interest.