A man was fatally stabbed at the Pentagon Metro station in Arlington, Virginia, Monday morning, according to officials.
The victim was stabbed on the station's lower level platform at about 9 a.m., according to Metro Transit Police, which responded with the Pentagon Force Protection Agency.
The man, who has not been identified, was pronounced dead at the hospital.
Police said "preliminary suspect information has been established and an investigation is ongoing."
A commuter told NBC News by email that she was at the station following the violence.
"I walked into the station and saw red stuff on the ground. I almost stepped in it, and looked over," said Lauren, who only wanted to be identified by her first name. "There was a man motionless on the ground, and Pentagon police with guns came running in."
"I moved away realizing the red stuff was blood, and that’s when I saw the large pool of blood," she said. "I hopped on a train really fast unsure of where the person who did it was and just trying to get to safety."
Tweets sent from Metrorail Info beginning at about 10 a.m. said trains were bypassing the Pentagon station due to a police investigation, affecting the blue and yellow lines, and buses were available.
This is a developing story; please check back for updates.