(NewsNation) — At least 850 murders across the United States over the past few decades are believed to be connected to long-haul truck drivers, according to the FBI’s “Highway Serial Killings Initiative.”

Frank Figliuzzi, a former FBI assistant director for counterintelligence, said Wednesday on NewsNation’s “Elizabeth Vargas Reports” that truckers who spend most of their time on the road are often the suspects.

The FBI initiative helps link murders that initially seem unrelated but follow a pattern of female victims, many involved in prostitution or sex trafficking, being picked up at truck stops, sexually assaulted and then killed, with their bodies dumped in different locations.

“The FBI is confident (the 850 killings) are the work of serial killers,” Figliuzzi said. “In fact, there are already 25 long-haul truckers who are in prison for multiple homicides.”

He said there are 200 killings still unsolved and 450 suspects being looked at in those cases.

“In my book, I tried to narrow that suspect pool down by getting deep into three subcultures: long-haul truckers, sex trafficking victims and crime analysis,” Figliuzzi said, referring to his new book, “Long Haul: Hunting the Highway Serial Killers,”

Figliuzzi spent a year riding more than 2,000 miles in a semitruck to research the subculture.

He described an isolating lifestyle where 10% of long-haul truckers drink alcohol daily, 20% binge drink regularly, and 44% experience clinical depression.

“Some of these killers, when interviewed, say it dawns on them that they now have the license to kill because the freedom is there to exploit those law enforcement jurisdictions,” Figliuzzi, who spent 25 years serving the FBI, said.

The FBI contends that while most truck drivers are hardworking Americans, the inherent isolation and transient nature of the job could draw serial killers or potentially create them.