Darren Vann, 44, of Gary, was arrested in 2014 and charged with strangling Afrikka Hardy, 19, and Anitha Jones, 35. Police said then that Vann told them where he could find the bodies of five more women.
He was charged with murder in the five other cases on Monday, Gary police Lt. Dawn Westerfield tells PEOPLE.
Westerfield adds that Vann was also charged in Lake County Superior Court with 10 additional counts including rape, criminal confinement and attempted murder on Monday.
Among the other victims are Teaira Batey, 28, Christine Williams, 36. Three of the victims remain unidentified.
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The 44-year-old told police that he began killing after serving five years in a Texas prison for rape in 2009, the Tribune reports.
"I feel I shouldn't have went to prison the first time," he said.
Police discovered Hardy's body in a Hammond motel room and connected Vann to her through an escort service website. A probable cause affidavit then stated that police identified Vann from surveillance video outside the motel.
The other victim's bodies were found in abandoned buildings in Gary.