COLUMBUS (WCMH) — To get to the truth, detectives have to go deep into the minds of a serial killer. They spend months, sometimes years investigating cases.

“These crimes are not committed in a vacuum,” said former FBI agent Harry Trombitas. “People see things, it is very hard to commit the perfect crime.”

Trombitas says killing sprees can often be triggered by stressors.

“A lot of times stressors will lead somebody, to something that is occurring in their life to act out and commit a murder. Then they might have another stressor, and that will come up, they feel the need to commit another crime. We see people that go for years between homicides,” said Trombitas.

The former agent served over 30 years in law enforcement. He says in cases like this, tips from the public can make a difference.

In 2003, Trombitas helped to solve the 270 “highway shooter” case.

“We had over 5,700 tips on that case. It was tip 5,444 that led to the resolution of the case.”

As for the Shawn Grate investigation, Trombitas suggest that the Marion County community speaks up.

“A guiding principle for people, if you see something say something. If you see something unusual we just ask the public to make contact with us.”