Gary Muehlberg, 74, already was in prison 28 years for a different murder case. Authorities say he's admitted killing two other people.
“I still dislike that negative, dark, short period in (my) past life,” Muehlberg wrote in a letter from prison to a police detective in suburban O'Fallon, Missouri.
KTVI reported four of Muehlberg's victims were killed in the early 1990s. He gained his nickname because the bodies were found in different kinds of containers.
Tuesday's guilty pleas were for the murders of Brenda Pruitt and Donna Reitmeyer.
Pruitt vanished in May 1990. Her body was found 17 months later in a trash can along a St. Louis County road.
Reitmeyer's body was found in a trash can inside the St. Louis city limits in June 1990.
- He strangled and violated a 74-yar-old man's corpse. It will cost him freedom for the rest of his life.
- A Convicted Killer Confessed to Murdering His Roommate. Cops Have Now Charged Him With 2 Murders — and He May Be Linked to Nearly a Dozen More.
- Suspect, 76, arrested in connection to cold case 1971 slaying of Massachusetts woman
Then Muehlberg pleaded guilty two weeks ago to murdering Sandy Little. Her body was stuffed inside a dresser, which was abandoned along a highway in suburban O'Fallon in February 1991.
DNA work by an O'Fallon officer connected Muehlberg to the cases with the most recent convictions.
Muehlberg is scheduled to enter another guilty plea next week. A hearing is planned in the March 1990 killing of Robyn Mihan.
Authorities say Mihan's body was sandwiched between two mattresses, which were wrapped with wire and left along a rural road.
The fifth case involving Muehlberg involves a victim who never has been found. Authorities say he admitted killing a woman at her home, then leaving the body in a metal barrel near a car wash.
The female victims reportedly were connected with a south St. Louis neighborhood known for prostitution. But a motive for Muehlberg's actions never has been revealed.
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