by KYW's Michelle Durham
The FBI Special Agents assigned to the Behavioral Analysis Unit see the toughest cases in country, and are called in by state and local police agencies across the country to help solve serial murders and rapes.
It's located in a secure, undisclosed location inside the FBI Training Academy in Quantico, Virginia.
One of the keys to finding a serial murderer or rapist , according to Unit Chief Mark Hilts, is to look for patterns.
"In the victim selection, is there some aspect or characteristic of the victim, some pattern that we see, that would help us know what type of a victim he's targeting."
And also what occurs on the crime scene is important, too.
"Activities that he does with the victims, and also activities that the offender might do that are not necessary that he feels compelled to do."
Here's what you don't know about serial killers:
"Every time there is a serial killer, some self proclaimed expert is going to get on the media and talk about how once they start killing they never stop. With some killers, that's true. But some killers have successfully stopped."
And Mark says he's never met a serial killer yet who left clues on purpose.
"Our experience is, no. If they wanted to get caught they could stand up raise their arms and give themselves up."
Hilts explains how he and the eight special agents who work under him on these cases manage not to take the horrific scenes they see home with them.