Police: School bus was picking up victim's brother when it fatally struck 6-year-old boy

A 6-year-old boy was fatally struck by a yellow school bus Wednesday in Williamsburg, police say.
The incident happened at South Fifth and Hooper streets around 8:30 a.m., according to police. 
They say the school bus was picking up the victim’s 9-year-old brother at the time. Police say the 6-year-old boy was running to try to get on the bus and stepped in front of it when he was struck.
An MTA bus driver later found the boy lying in the street and called their dispatcher and 911, police say. 
Police caught up with the school bus driver, who was still on his route. They say they believe preliminarily that the driver did not know that he struck the child.
The bus’s mechanical system is also being thoroughly checked, according to police. 
The MTA tells News 12 that hearts at the agency go out to the family and to their driver who came across the child in the street.
They say they are fully cooperating with the NYPD and helping their driver who is experiencing trauma.
Neighbors say they're in shock. Mildred Peralta says she has lived in the area for 50 years and can’t imagine what the family is going through.
“Being a parent, it hurts me really bad because any mother cannot even believe or imagine that bring a child to this world and this could happen,” Peralta says. 
News 12 attempted to reach out to the school that the bus is contracted for comment.