The man charged with fatally setting a woman on fire as she slept inside a subway car in Brooklyn has pleaded not guilty to charges including murder, prosecutors say.

Sebastian Zapeta, 33, was arraigned Tuesday on charges of first-degree murder, second-degree murder and first-degree arson in connection with the death of 57-year-old Debrina Kawam last month.

“It is difficult to fathom what could lead someone to commit the atrocious and horrific murder with which this defendant is charged,” Brooklyn District Attorney Eric Gonzalez said in a statement. “My office swiftly obtained an indictment, and we are determined to exact the most severe punishment for this heinous and inhumane act.”

“Ms. Kawam and her loved ones deserve a measure of justice and New Yorkers deserve to feel safe in the subways,” Gonzalez added.

Kawam was sleeping on an F train as it reached the Stillwell Avenue station in Coney Island around 7:25 a.m. on Dec. 22, according to the DA’s office.

Zapeta, who was riding in the same train car as Kawam, was caught on surveillance tape using a lighter to set fire to fabric that was covering her while she slept, the DA’s office said.

Authorities said Zapeta fanned the flames with a shirt, leaving Kawam engulfed in the blaze. Then, prosecutors said he sat on a platform bench and watched as she burned before walking away.

Police said Kawam was pronounced dead at the scene. The city’s medical examiner said she died due to a combination of heat burns and smoke inhalation, according to prosecutors.

Zapeta was arrested later that day after police received a tip that he was riding an F train near the 34th Street-Herald Square subway station in Manhattan, the DA’s office said.

Kawam’s body was only identified nine days after she died, as she was “burned beyond recognition,” the DA’s office added.

Zapeta, who is being held without bail, is set to appear in court again in March. If convicted, he faces a maximum sentence of life in prison without parole.