Lois Castle, 58, committed suicide at home with a revolver yesterday. Two police officers heard a single gunshot as they were about to knock on her front door. They were at her house to arrest her for the 1970 murder of her young stepdaughter. Castle apparently realized that she was going to be arrested. Only a month earlier she had been interviewed by detectives about Dorothy’s death 35 years ago.

In 1970, Castle told police that the girl had fallen out of a tree she was climbing and hit her head on a rock. But Dorothy’s natural father, Dwayne, who was married to Castle at the time, thought his wife was lying. “She said she would hurt me if I bother her again,” Dorothy had told her father earlier.

“Your little girl is making up stories about me. I try to love her, but she rejects me,” Castle told Dwayne.

An autopsy was inconclusive, and the death was ruled accidental. Dwayne divorced Castle shortly thereafter.

But the case was reopened recently when a playmate of Dorothy’s came forward. Beverly Lisenby, also seven at that time, said she was about to knock on the door of Dorothy’s house that fateful day. But instead of knocking, she listened quietly as she heard Dorothy screaming for help and Castle telling her to shut up. Beverly listened until it was silent inside, then ran back home. She was so shaken by the event that she had told no one in all these years.

The coroner dug up Dorothy’s body and did a second autopsy. Using new crime-solving tools, he determined that Dorothy had been struck in the skull several times by a rock the size of a baseball.

The police are now trying to locate Dwayne to tell him the good news.