At least 10 people were shot and at least 6 more were injured while riding the subway in Brooklyn Tuesday morning, New York law enforcement and fire department officials have confirmed.

Officers were called around 8:30 a.m. to Sunset Park’s 36 Street station, where they suspect a smoke bomb was detonated and a gunman shot victims from inside a train, reports The New York Times. A law enforcement official said authorities are looking for a heavyset man carrying a gas mask and wearing a worker’s vest.

No MTA workers were physically harmed, The Associated Press reports, per the Transport Workers Union Local 100, and there were no active explosive devices found at the scene, according to the New York Police Department (the fire department had said earlier that “several undetonated devices” had been found).

Disturbing video of the incident shows smoke and passengers spilling out of a subway car upon arrival at a platform. Some then scream and run panicked to an exit, while others stay to help those who were hurt.

Schools in the area were subsequently told to lock down and shelter in place.

“My subway door opened into calamity,” one witness said, per AP. “It was smoke and blood and people screaming.”

Police were still searching for the suspect as of 12 p.m. Tuesday. The incident is not currently being investigated as an act of terrorism, the NYPD initially said.

Five of the victims are in critical condition, but none of them sustained life-threatening injuries, the Times writes per the fire department.

This is a breaking news story that will be updated as more details become available.