A semiautomatic Glock handgun was found inside the subway station where more than a dozen people were injured following a mass shooting aboard a rush hour train on Tuesday morning, two law enforcement sources told Gothamist.

The gun was jammed, according to one senior law enforcement official, suggesting the shooting could have been even worse.

The suspect, who remains at large, was wearing a gas mask and green construction vest. Police said he first detonated a smoke device aboard a rush hour N train as it pulled into the 36th Street station in Sunset Park headed toward Manhattan.

Read more: 10 people shot, six others injured in Brooklyn after subway shooting

As the Manhattan-bound train filled up with smoke, the man began shooting, striking at least 10 people, officials said. Five of the victims suffered critical injuries, though all were expected to survive.

Six other people were hospitalized with non-shooting related injuries, including smoke inhalation or wounds sustained while running from the scene, according to an FDNY spokesperson.

Speaking at a press conference on Tuesday afternoon, Governor Kathy Hochul said New Yorkers should continue to exercise caution.

"This person is dangerous. We’re asking individuals to be very vigilant and alert,” Hochul said. “This is an active shooter situation right now in the city of New York."

The suspect’s whereabouts and motivation remain unknown. The NYPD is not currently investigating the incident as an act of terrorism, according to NYPD Commissioner Keechant Sewell. Police are expected to provide another update later in the day.