The Brief An undocumented immigrant is facing federal charges after a shooting on a MARTA bus last week in Sandy Springs, according to the U.S. Department of Justice. Guillermo Cruz Velazquez, 53, was riding a MARTA bus when a gun in his bag allegedly fired a single bullet, hitting him and a woman on the bus. A bloody trail led the Sandy Springs Police to the suspect after he ran off the bus following the shooting. Authorities have identified an undocumented immigrant from Mexico as the suspect facing federal charges after an accidental weapon discharge inside a MARTA bus left two people injured last week. What we know:Guillermo Cruz Velazquez, 53, originally from Iztapalapa, Mexico, was riding a MARTA bus when a gun inside his bag allegedly discharged.