CHICAGO (CBS) — A convicted sex offender who allegedly confessed to at least seven murders in northwest Indiana has told police his crimes date back as long as two decades.

Gary resident Darren Vann, 43, has been charged with murdering 19-year-old Afrikka Hardy. Hammond Police Chief John Doughty said charges were possible in at least six other murders which were still under investigation.

According to Doughty, Hardy was a prostitute who met Vann on Friday at the Motel 6 in Hammond. Police said Vann responded to an ad Hardy and her facilitator placed on backpage.com, and arranged to meet Hardy Friday night.

The woman who facilitated the meeting called police when she received suspicious text messages from Hardy’s phone. Fearing for Hardy’s safety, she called a male friend and went to the hotel, where they found Hardy’s body, and then called police.

Afrikka Hardy (Credit: Facebook)

Afrikka Hardy (Credit: Facebook)

Doughty said the woman who facilitated the meeting provided investigators with Vann’s phone number, and police tracked him down to Gary. When he was arrested, he confessed to killing Hardy, and told detectives he “messed up” by committing the crime in Hammond, Doughty added.

Vann later told police about six other victims, whose bodies all were found in abandoned homes in Gary.

A source told CBS 2’s Brad Edwards that the suspect has indicated that there may be many other victims, including those in other states, but Doughty said police have not confirmed any victims beyond the seven found so far.

Doughty said Vann — who is a convicted sex offender in Texas — has been cooperative from the beginning, and told police his crimes “could go back as far as 20 years,” although the victims found so far all appear to have been killed more recently.

Vann apparently only wanted to discuss the Indiana cases because the state has the death penalty and he wants to be executed for his crimes, the sources told Edwards. Doughty would only say Vann “was looking for a type of deal with the prosecution.”

Vann has lived in Northwest Indiana since 2004, mostly recently in Gary, according to Gary Police Corporal Gabrielle King.

Teaira Batey (photo provided)

Teaira Batey (photo provided)

Three of the victims found in Gary have been identified: 28-year-old Teaira Batey and 36-year-old Kristine Williams, both of Gary; and 35-year-old Anith Jones, of Merrillville. The other three victims have only been described as African-American women.

Marvin Clinton says Batey, his fiancé, had been missing since January.

He got the news Monday that Batey was one of the unidentified bodies found in a vacant house in Gary. Clinton and Batey have a young son together, who has not been told.

“She was a good person, friendly happy, all around a good person,” said Sam Palm, Batey’s neighbor.

Anith Jones, one of at least seven women whose bodies were found in northwest Indiana over the weekend. (Credit: Gary Police)

Anith Jones, one of at least seven women whose bodies were found in northwest Indiana over the weekend. (Credit: Gary Police)

Hardy and at least one other victim were strangled. Autopsies were pending for the other five.

“I just can’t believe that she’s gone,” Yolanda Mosley, the victim’s aunt. “It’s just unbelievable that this man has been running around doing this for so long.”

Family members say Hardy wanted to be a doctor and was trying to get back into school, but they fear she got caught up in the wrong crowd.

Jones had been missing for a week before her body was found in Gary. Doughty said there were no missing person’s reports for the other victims who have been identified.

Doughty said investigators have not yet determined Vann’s motive.

“I don’t have a specific reason he does this,” he said.

He also could not say why Vann was so quick to cooperate with the investigation.

“It was just something he wanted to do. That’s all I can say,” he said.