Kelsey Grammer provided shocking details of his sister’s last moments before she was murdered … talking about the abuse she suffered before she was stabbed to death — weeping while reading from the book he wrote about her.

The famed television actor opened up about his sister’s killing during an ABC News interview while promoting his new book “Karen: A Brother Remembers” — a memoir dedicated to keeping his sister’s memory alive and telling more of her story than just the way she died.

Watch the clip for yourself … Grammer tells Diane Sawyer that after his sister was abducted, in 1975, she was taken to a nearby house, where the men who grabbed her took turns raping her.

A man named Freddie Glenn was arrested and later convicted of the murder. He’s serving a life sentence … and, Kelsey says he plans to oppose his parole each time it comes up, as he has in the past.

In a separate interview with People, Kelsey admitted his sister’s loss drove him to drugs and alcohol. He was arrested for drunk driving and cocaine possession multiple times between 1988 and 1996, during the height of his fame on “Cheers,” and later on “Frasier.” He’s since gotten sober.