The impact sent the 33-year-old NYPD traffic agent flying into the path of a 5-ton yellow school bus and pinned her underneath.
About 30 strangers converged from all directions to lift the bus off her body - a superhuman effort that was too late for her, but managed to save the life of her child.
Sanz was rushed to a nearby hospital, where doctors delivered her baby boy by Caesarean section. Sadly, Sanz died about an hour later after giving birth to her son.
Doctors say the 3-pound, 6-ounce infant's condition has been upgraded from critical to stable condition on Saturday morning.
"This is such an unbelievable tragedy that took place, it took away one of our own," said James Huntley, president of the union that represents traffic agents. "But I'm so thankful to the city of New York and to the citizens who came to her aid, like real heroes out of a comic book."
The 72-year-old van driver, Walter Walker, pleaded not guilty Friday to charges of criminally negligent homicide and aggravated unlicensed operation of a motor vehicle. He was being held on $100,000 bail. His defense attorney didn't immediately return a phone call.
Police said in a court filing that the brakes on Walker's van had deteriorated so badly it was unsafe to drive. Walker told investigators he'd had some repairs done six months ago, but knew there were still some problems.
Walker has a long history of driving offenses and arrests dating back to the 1980s. Police said his license had been suspended 20 times, mostly recently for failure to pay parking tickets. He had previously been sentenced to probation and fines for his driving offenses.
Mourners and neighborhood residents gathered outside the hospital Friday to pray for Sanz and her newborn child, named Sean Michael.
Sanz, a Bronx resident, had been a civilian member of the NYPD for two years, one of the city's blue-uniformed traffic agents who direct vehicles, write parking tickets and operate tow trucks - without benefit of guns or bulletproof vests.
She had been on administrative duty because of her pregnancy when she went out to lunch and crossed the street, just at the moment when the van ran the light.
A passenger in Walker's van gave an account of the accident.
"We was riding along, coming down the hill," said John Dargan. "He said, 'Oh, my Lord, I don't have no brakes.' It happened so quick. I just closed my eyes."
Walker said, "The light turned red, and I couldn't stop. I tried to miss her." He said he had been using his brother's van to help a friend move.
Bystanders, including Gary Burgess, came in waves to lift the mini school bus from Sanz's body.
"It was the human thing to do," said Burgess, 50. "I had grease on my hands, but I did this from my heart."
There were no children on the bus at the time.
Sanz survived the delivery in an emergency operating room at St. Barnabas Hospital but died about an hour later, spokesman Fred Winters said.
The baby was taken to the neonatal intensive-care unit and placed on a ventilator. He upgraded to stable condition Friday night.
At the hospital on Thursday, Mayor Michael Bloomberg met with Sanz' husband, Rafael, to offer his condolences.
"It's a terrible poignancy that Donnette's son's birthday will now coincide with the day his mother died," the mayor said. "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."
Pedro Espada Jr., who runs a health care network with an office near the site of Thursday's accident, has started a special fund for the infant, with an initial contribution of $1,000 from his company.
To contribute to the fund set up for the little boy:
Sean Michael Sanz Fund
Soundview Healthcare Network
731 White Plains Road
Bronx, NY 10473
718-589-2232
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