His crimes gained international media attention when the district attorney falsely alluded to cannibalism.

[2] He committed his first violent offense in November 1961 at age 17, when he broke into a house and attacked the occupant, a teenaged girl.

[4] During the search, police discovered the remains of Susan Perry, who had been missing since the previous Labor Day (September 1968).

[3][4][5] Police knew that the clearing where the bodies were found was used by Costa for growing marijuana, making him their main suspect.

[3] Costa knew the four women, who had all disappeared following his return to Truro, and his fingerprints were on the torn cover of the Volkwagen's owner's manual, which was found in the woods.

"[7] Costa was considered as a potential suspect in the deaths of 16 women on the West Coast of the United States.

[8] This included Bonnie Williams and Diane Federoff, hitchhikers he had picked up while crossing the country in 1966, and his girlfriend in San Francisco, Barbara Spaulding.

[10] In May 1970, he was convicted for the murders of Wysocki and Walsh and sentenced to life in prison at Massachusetts' Walpole Correctional Institution.

[8] In 2021, Liza Rodman co-wrote the book The Babysitter: My Summers with a Serial Killer, about her encounters with Costa during her childhood.