EDINBURG -- A teenager accused of shooting a federal agent near the U.S.-Mexico border will face an attempted murder charge as an adult, a Texas judge ruled Tuesday.Marquez Alvarado, 17, is accused along with his older brother and father of ambushing a U.S. Immigration and Customs Enforcement agent last summer. Prosecutors allege the father woke his two sons in the middle of the night, saying there was a suspicious vehicle down the road, and the trio chased and shot at the vehicle before it ran off the road.State District Judge Jesse Contreras certified Alvarado, who was 16 at the time of the shooting, as an adult and set his bail at $50,000. Alvarado will have to be indicted by a grand jury, but Contreras said there was enough evidence to support the attempted murder charge.Investigators allege that Pedro Alvarado woke two of his sons the night of July 3, and that both teens grabbed guns and climbed into their father's truck. With the elder Alvarado behind the wheel, they chased a silver Jeep Grand Cherokee more than two miles until it ran off the road.The vehicle was hit by gunfire multiple times, and its driver, ICE agent Kelton Harrison, was shot once in the back. The bullet remains lodged in his back. Harrison had been conducting surveillance in the area as part of a long-running drug-trafficking investigation. No one has suggested that the Alvarados knew the driver was a federal agent.Contreras on Tuesday told Marquez Alvarado that he made a "big mistake" and that the seriousness of the crime required that he be moved into the adult criminal system."It's not over for you," Contreras said. "You still have a long life ahead of you."The teen's attorney, Ricardo Flores, said later that his defense was constrained by the fact that he couldn't call his client's father or brother to testify. After the judge's decision, the teen -- who was handcuffed and shackled -- embraced his mother in the back of the courtroom."We're trying to get the necessary resources to bond him out," Flores said.A county juvenile probation officer testified Friday that Marquez Alvarado was well-behaved during his months in detention.