CHICAGO (CBS)– Nearly a year after three Indiana children were hit-and-killed, steps from getting on their school bus, the woman accused of killing them is going to trial.

Police say 24-year-old Alyssa Shepherd was behind the wheel of her truck, speeding on her way to work through Rochester, Indiana, when she went around a school bus with its stop sign out. She hit four children crossing the street.

Brothers Xavier and Mason Ingle, and their big sister Alivia died.

A fourth child, Maverick Law survived.

Shepherd’s trial starts Tuesday. She’s facing 21 years in prison.