Mayor Michael Bloomberg says the infant son of a pregnant traffic agent who was killed by a runaway van last week has died.

The baby, Sean Michael Sanz, was delivered by a Cesarean section two months prematurely after his mother, 33-year-old Donnette Sanz, was pinned under a school bus. He weighed just 3 pounds, 6 ounces.

?It?s very shocking because he was our miracle baby, we were hoping our baby will survive,? says Carmen Sanz, the infant?s aunt. ?Right now he?s in heaven with his mother, and they will be buried together.?

The boy?s mother was struck by the van when she was crossing the street on her lunch break last Thursday. The impact sent her flying into the path of a yellow school bus and pinned her underneath.

About 30 bystanders rushed to Sanz?s aid and lifted the 5-ton bus. Sanz, who was seven months pregnant, was rushed to St. Barnabas Hospital in the Bronx where doctors performed an emergency delivery of the baby, but were unable to save the mother.

"We are deeply saddened by the loss of Sean Michael Sanz so soon after his mother Donette, whose service to the City of New York and the police department will never be forgotten,? says Police Commissioner Ray Kelly. ?Our hearts and prayers are with their family."

The driver of the van that struck Sanz, 72-year-old Walter Walker, has been charged with criminally negligent homicide and aggravated unlicensed operation of a motor vehicle. Police say Walker?s license has been suspended 20 times in the past.