CHICAGO (CBS) — It’s a CBS 2 exclusive.

Investigators now believe Bruce Lindahl murdered at least 12 people. Until today, only four were confirmed.

And for the first time, police are revealing decades-old crime scene photos.

CBS 2’s Mike Puccinelli goes inside the case files.

Detective sergeant Caleb Waltmire is working a murder case that happened nearly forty years ago. It’s the case of Debra Colliander who was found buried in a Kendall County field back in 1982.

But two years before that, she was raped by suspected serial killer Bruce Lindahl. Two weeks before Colliander was set to testify against Lindahl, she disappeared.

When asked if Lindahl killed Colliander, Detective Sergeant Caleb Waltmire said yes.

“Personally, I think the case is very strong that he did,” Waltmire said.

But proving that will be difficult because DNA evidence from Colliander’s killer was not preserved.  Back in 1982 when a farmer saw an indentation in his field, he took out a spade and started digging and found the remains of Debra Colliander.

But while DNA evidence is lacking in the Colliander case, Lisle police had DNA from the sexual assault and murder of 16-year-old Pamela Maurer.

Lindahl died in 1981, accidentally killing himself while stabbing a man to death.  After exhuming Lindahl’s body, they positively linked him to Maurer’s murder.

And now they’re certain he left behind many more victims.

“I would say up to 12,” said Waltmire.

In the past three months, the Lisle Police Department Investigators compiled a map showing where unsolved rapes and murders happened. And the crimes and body locations are all surrounding known Lindahl addresses.

“So it establishes that when he was living in the Lisle-Woodridge area, he hunted in the area,” said Detective Chris Loudon.  “When he moved to Aurora, he hunted there.”

Now after providing some closure for the family of 16-year-old Pamela Maurer, they’re determined to do the same for the loved ones of other victims.

“There’s a lot of work to be done,” Loudon said. “We know this monster. Now we need to find out who are the other victims of this monster. ”

Tips have been flooding in since Lindahl was identified as Maurer’s killer on Monday.

But police want to hear from you if you have any information about Lindahl or possible victims.