Diana Rocco

DEPTFORD, N.J. (CBS) – Authorities say a New Jersey woman has died after her grandson’s wife allegedly poisoned her with antifreeze.

Anna Castagna, 43, of Brooklawn, New Jersey, is facing several charges, including one count of first degree homicide, in connection with the alleged poisoning by antifreeze of her husband’s 88-year-old grandmother Mary Groatman.

“It has been determined she researched the affects of antifreeze on the human body in the time period leading up until this incident,” said Gloucester County prosecutor Sean Dalton.

Costagna was Mary Groatman’s primary caregiver. She lived in her Brooklawn, Camden County home with her husband and two kids for a decade. Last week, Groatman was placed in a Deptford rehab center after a fall. On Sunday, staff there found her unresponsive.

The crime is alleged to have occurred on August 19th.

“In the late morning of August 19th, the accused purchased antifreeze and went for a so-called visit to the rehab center where she caused Mrs. Groatman to ingest the antifreeze ultimately resulting in her death,” said Dalton.

Etholine Glycol, the main ingredient in antifreeze, was found in Groatman’s system. On Thursday afternoon, she was taken from life support.

There was no answer at the family home, but neighbors say they’re shocked by the allegations. They’ve known Costagna for years. She used to babysit for families in town for extra money and she appeared to care for Groatman as she would her own grandmother.

“She would always take her to the doctor and the grocery store. She would help around the house,” said Danielle Prioli, who is friends with Castogna’s 15-year-old daughter.

“She was just a genuinely nice person. Never had anything bad to say about anybody,” neighbor Christine Prioli said.

Castagna is being held at the Gloucester County Jail on $350,000 cash bail and is facing 30 years to life in prison if convicted.