A veteran NYPD detective’s teen daughter recalled her Brooklyn basement resembling a horror movie when she encountered her cousin stabbing her dad during a bloody fight two years ago.

“It looked like a horror film. My first reaction was to stop him from hurting my dad,” Desiree Morales, 18, wrote in a letter read in Brooklyn Supreme Court on Friday, just before Angel Rosario was sentenced to 20 years in prison for the Dec. 20, 2013, attack.

Rosario, 66, was convicted of first-degree assault and reckless endangerment for stabbing Peter Morales, a 20-year detective, in the head, abdomen and neck.