Police are investigating the stabbing death of a 14-year-old at a subway station in Harlem.

A 14-year-old boy was fatally stabbed on a New York City subway platform on Saturday afternoon, police said.

Police believe an altercation began above ground near the 137 St.-City College station in Hamilton Heights before it moved into the subway station, where the victim was reported to have been stabbed in the abdomen on the northbound 1 line platform around 3 p.m. Police later recovered a knife and a broomstick at the scene, officials said.

A witness to the stabbing told BBC News reporters that “his lips were purple and his eyes were rolled back, and he was bleeding a lot of blood,” adding that he saw a group of teenage girls run out of the station. “They wanted to take his phone.”

The teenager was pronounced dead at Mount Sinai Morningside Hospital, police said, adding that they are waiting to identify him until after his family has been notified.

Police identified a "person of interest" later Saturday in the area of West 173rd Street and Broadway based on security video from the subway station. The person, who had injuries to his back, his abdomen and his left hip, was transported to NewYork-Presbyterian/Columbia University Irving Medical Center and was stable, police said.

Officials were questioning that person, adding that his involvement was unclear, that there have been no arrests and that the investigation is ongoing.

At a news conference on Saturday night, New York Police Department Transit Chief Jason Wilcox said that police believe the two people involved in the incident knew each other and that no other suspects were being sought.

Mayor Eric Adams said the stabbing "really highlights why we need the lights on in schools like this,” according to NBC New York, adding: “We need to find out what happened. We’re going to find out the person responsible.”

Officers closed the Hamilton Heights station on Saturday to conduct their investigation, NBC New York reported. Service to the station had resumed by 10:30 p.m.

Richard Davey, the president of New York City Transit, called the incident "senseless and tragic" in a statement and said Metropolitan Transit Authority officials are cooperating with the police investigation.