BOISE -- Murder charges have been filed against a Texas man who was pulled over east of Boise while driving a van belonging to a man who had found dead after a camping trip.

In addition to first-degree murder, 25-year-old Jeffrey Maynard is also charged with aggravated robbery, identify theft, and aggravated motor vehicle theft.

Investigators for the District Attorney's Office covering Colorado's Gilpan and Jefferson counties say they believe Maynard killed 62-year-old John Cumby Jr. about two weeks before Ada County deputies stopped him in Cumby's blue Plymouth van Sept. 10.

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Cumby, a resident of Rock Falls, Illinois, had traveled to the Denver area in August for an extended camping trip. His family reported him missing after he failed to return in early September as he had planned.

Cumby's body was found in the Moffat Tunnel, a railroad tunnel that cuts beneath the Continental Divide in Gilpan County, on Sept. 13. An autopsy revealed he had been strangled.

DA's Office Investigator Troy Cooper said it does not appear Maynard and his victim knew each other before the slaying.

"The only theory was that they met each other while camping," he said.

It's unclear whether the suspect attacked Cumby immediately after coming upon his camp, or if the men spent time together after meeting. A motive in the murder is also unknown, Cooper said.

Maynard was carrying Cumby's wallet, ID and other possessions when he was pulled over for erratic driving east of Eisenman Road on Interstate 84 Sept. 10.

Deputies with the Ada County Sheriff's Office said Maynard was swerving back and forth between lanes and cut off a semi truck just before he was stopped. The suspect was unable to tell deputies why he was driving Maynard's van, or where the other man was.

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When a deputy asked Maynard to get out of the vehicle, he grabbed a can of mace from between his legs, but dropped it after the deputy noticed what he was doing, according to the sheriff's office.

Maynard was booked into the Ada County Jail, where he remains on a $500,000 bond. Cooper said the DA's office will seek to extradite him back to Colorado to face charges in Cumby's death.

In addition, Maynard has active arrest warrants out of Texas on charges including theft and attempted arson.