Updated

A writer was savagely beaten to death in her Midtown apartment yesterday, a gruesome attack caught on a harrowing 911 recording — and cops arrested her teenage son, authorities said.

Karyn Kay, 63, made the call at about 9:30 a.m. to get help for her 19-year-old son, Henry Wachtel, who was suffering from a seizure, sources said.

But as she tried to help him, he suddenly turned on her and allegedly beat her to a bloody pulp inside their West 55th Street apartment, the sources said.

“Help! Help! He’s attacking me! Help!” Kay desperately screams on the 911 recordings.

Sources said the teen could be heard on the 911 call loudly grunting as he allegedly pummeled his mother.

Click here for more on this report from the New York Post.