In the F Train at Coney Island-Stillwell Avenue, A Guatemalan migrant lit a sleeping woman on fire with a match, causing the victim to burn alive and die at the scene.

The horrifying attack occurred early Sunday morning at the Coney Island-Stillwell Avenue station, around 7:30 a.m. Surveillance footage later showed the suspect calmly sitting across from the victim as flames consumed her, burning her clothes completely off.

Police briefly spoke with the man shortly after the attack—unaware at the time that he was the suspect—and allowed him to leave. He was ultimately apprehended near 34th Street when a witness recognized him riding another train. Authorities say it was only upon reviewing footage and witness statements that officers realized they had previously encountered the alleged killer and failed to detain him.

The victim’s identity has not yet been released. The NYPD is investigating the motive behind the deadly assault, and the suspect faces murder charges in what officials are calling one of the most disturbing subway crimes in recent memory.