A Flatbush man is facing a second-degree murder charge for allegedly shooting his girlfriend, according to police and sources close to the victim.

Tahj Nelson, 23, was taken into custody on Monday. He is accused of shooting Tatiana Pettus, 24, inside their Flatbush apartment on the night of June 30. Court documents reveal that Nelson's mother was present that night.

The NYPD says officers responded to 2817 Foster Ave. just before 11:30 p.m., where they found Pettus with a gunshot wound to her neck. Paramedics rushed her to NYC Health + Hospitals/Kings County, where she died.

Nelson faced a judge for the first time Tuesday and pleaded not guilty, according to the Brooklyn District Attorney's Office.

Court documents say Nelson and his mother Lillian were alone in the living room when he allegedly told her that he didn't want her there.

The criminal complaint says Lillian heard a gunshot ring out and asked Nelson, "Why did you do that?"

He responded, "I'm sorry, Mom," and she replied, "Go."

Nelson is also charged with second-degree criminal possession of a weapon.

He is due back in court Friday.