NEW YORK (AP)  -- A pregnant NYPD traffic agent died after being crushed under a 5-ton school bus that a group of horrified bystanders lifted off the woman in a heroic effort that allowed doctors to save the baby.

Thirty-three-year-old Donnette Sanz was seven months pregnant when she was struck crossing the street Thursday in the Bronx by a van that pushed her in front of the bus, police said.

Doctors at nearby St. Barnabas Hospital saved Sanz' 3-pound, 6-ounce son by emergency Caesarean section. His mother was pronounced dead shortly after his birth. The boy was in critical condition late Thursday.

The driver of the van, Walter Walker, was arrested on charges of criminally negligent homicide and aggravated unlicensed operation of a motor vehicle, police said.

``My brakes went out,'' Walker, 72, told the New York Post in Friday editions. ``The light turned red, and I couldn't stop... I tried to miss her,'' he told the tabloid shortly after the accident.

``I tried to go behind her, but she stopped and moved back, and I hit her,'' Walker said, gripping his head in his hands. ``I feel bad, terrible.''

Police Commissioner Raymond W. Kelly said that Walker had ``20 suspensions'' to his driver's license. Walker told the Post that he did not have a driver's license because he couldn't pay parking tickets.

Mayor Michael Bloomberg met with Sanz' husband, Rafael, at the hospital, where he offered his condolences.

``It's a terrible poignancy that Donnette's son's birthday will now coincide with the day his mother died,'' Bloomberg said in a statement. ``I hope that as this child grows up, he comes to understand that his mother gave her life in service to our city, and that we are forever grateful.''