Penny Chapman pleaded guilty Tuesday to numerous counts of aggravated assault and related charges for the shooting last June.
Incredibly, no one was injured.
Authorities say the shooters were waiting for the bus after Chapman made a call following a confrontation with a male passenger who accused her of abusing her son.
Surveillance video showed two men firing on the bus, with bullets crashing through the windows. The shooters continued to fire wildly while retreating as the bus driver hit the gas and headed for Temple Hospital while calling police.
Two cousins who admitted shooting at the bus face 15- to 30-year prison terms. Bus-mounted cameras recorded the men brandishing guns and passengers hitting the floor.
A third person is awaiting sentencing and three others await trial.