A high school senior is accused of participating in a deadly armed robbery in December. San Antonio police arrested 18-year-old Joshua Castro on Wednesday at Holmes High School. Police say Castro and 18-year-old Sebastian Toledo shot and killed two people at a Circle K on Potranco Road near Richland Hills Drive. They reportedly pretended they were interested in buying a gun the victims were selling. Toledo killed himself on Monday night as police closed in on him. Castro is charged with capital murder.