A Harlingen man admitted to robbing a convenience store at gunpoint after he was caught with seven grams of marijuana.
Alberto Martinez-Valles was in police custody for possession when he confessed to the June 28 robbery.
Police arrested the 21-year-old on Friday night when they found the marijuana in his car.
The next morning Valles was questioned by investigators about the June 28 Valero Convenience Store robbery.
According to authorities, a male suspect entered the store, pointed a gun at the clerk and demanded money from the register.
Police said the suspect struck the store employee twice on the back of the head with the handgun.
During the interview, Valles made his confession.
He was charged with possession of marijuana and aggravated robbery.
His bonds total $250,500.