BOZEMAN, Mont. -

The FBI is now involved in the case of Kevin Briggs, the Bozeman rape suspect who escaped from the Law and Justice Center on February first.

Federal prosecutors filed a new charge of Unlawful Flight to Avoid Prosecution, because they believe he's fled Montana.

The federal court document details how Briggs is spotted on video surveillance at the Missoula Greyhound bus station the night of Saturday February first.

Bozeman Police arrested Briggs early in the morning that same day on four felony charges- including attempted rape and aggravated assault.

But Briggs walked away from the Bozeman Law and Justice Center after a police oversight left him unattended.

In the charging documents, an FBI investigator said someone admitted to dropping Briggs off at the Greyhound station, after driving Briggs from Bozeman to Missoula.

That person told police Briggs detailed his getaway plan during their drive.

First, Briggs said he'd head to Spokane, Washington. Then, Seattle.

Briggs reportedly said he would stay at homeless shelters and hoped to scrape up enough money to continue traveling.

From there, the person told investigators that Briggs planned to move south through Oregon, California and ultimately Mexico.

Eventually, Briggs said, he'd take a ship to Russia because he didn't think he'd be able to get extradited from there.

That person then said they gave Briggs money for a bus ticket to Spokane, before leaving him at the Greyhound station.

A Missoula resident told police he let Briggs stay in his garage that night before the bus trip.

The next morning is when investigators spot Briggs on surveillance video again at the Missoula Greyhound station, apparently boarding a west bound bus around 10 am on February second.

The FBI said Briggs has family in Oregon and previously ended up in California after a felony escape charge in 2006 out of Powell County.

The court documents state Briggs planned to dye his hair black and grow out facial hair so he wouldn't be easily recognized.

Kevin Briggs should be considered armed and dangerous. Anyone with information on his whereabouts should call 911.