BATAVIA, N.Y. -- A New York state stepmother was arrested Thursday and charged with murder for allegedly killing her 2-year-old stepson by pouring poison in his juice.

Melissa Englehardt, 24, is accused of first-degree manslaughter in the death of Andrew Cianfrini four months ago.

Her arrest came as a shock to Batavia residents who find the allegations disturbing.

"It's so sad what's happening in this world?" resident Peg Fryer said.

Andrew lived with his mother, Kristen Cianfrini, in Batavia, but had arranged visitations with his biological father, George Englehardt, and his wife in Elmira.

The baby was there on a visit when he died last fall.

Initially, the H1N1 virus was suspected.

"You know, you start thinking what are the possibilities and at that time there was a lot of talk about swine flu, talk that it could be swine flu but the medical examiner did a great job and in a week's time advised us ..that wasn't the case here," Batavia Police Det. Sgt. Patrick Corona said.

While Batavia police assisted in the case, Elmira detectives led the investigation and are limited in what they can say.

Sources say Melissa Englehardt is pregnant, possibly with twins, and poured antifreeze into her stepson's juice to poison him.

At this time, police do not believe Andrew Englehardt was involved in his son's death.