Philip Husereau strangled 5 girlfriends in New York and Nevada during S&M sex between 1983 and 1984. He died the same way (autoerotic asphyxia) on February 18, 1988. The next day, his sister told police that Philip had told her how he killed his last 5 girlfriends.

Husereau, Philip (? - 1988)

The accidental death of Philip Husereau, on February 18, 1988, was no more curious or twisted than the drifter's life. Police in Rochester, New York, report that Husereau was suffocated while engaged in masturbation, with his head inside a plastic bag of nitrous oxide "laughing gas."

Next day, his sister told authorities of Husereau's confessions in the deaths of five successive girlfriends, during 1983 and '84. 

His victims included Phyllis Weathers, a cocktail waitress and topless dancer whose body was found on a vacant lot in Las Vegas, Nevada, on August 10, 1984.

According to Husereau's confession, kept secret by his sister while he lived, the murders occurred during sex, when Husereau lost control of himself and strangled his partners or beat them to death.

Michael Newton - An Encyclopedia of Modern Serial Killers - Hunting Humans

SEX: M RACE: W TYPE: N MOTIVE: Sex./Sad.

MO: Strangled girifriends during sex; confessed to sister

DISPOSITION: Accidental death during autoerotic asphyxia, Feb. 18, 1988