NEW YORK (October 25, 2012)—A mother returned to her New York City apartment Thursday evening and found her two small children, ages 3 and 5, stabbed to death in a bathtub and their nanny with a knife in her hand, police said.

Police said the nanny had a self-inflicted wound.

The mother called 911.

The nanny was arrested and hospitalized.

It's unclear how many times the children were stabbed.

The New York Police Department is investigating.