A Marine based at Quantico, Virginia, and his brother were found dead in their car in Arizona after reportedly leading authorities on a lengthy chase before their car was disabled.

Authorities say the deaths of 36-year-old Travis Twiggs and 38-year-old Willard Twiggs appeared to have resulted from a murder-suicide.

Pinal County Sheriff's spokesman Mike Minter says the men had been sought since they reportedly carjacked a couple at the Grand Canyon on Monday night. Officers spotted the car and disabled it with spike strips, but say they heard gunshots as they were approaching the vehicle.

Authorities say Travis Twiggs was recently an active-duty member of the military based at the Marine Corps base at Quantico. Twiggs suffered from post-traumatic stress disorder and was reportedly unpredictable.

Will Twiggs was from Louisiana.