Police are investigating the death of a baby found unresponsive in a bathtub Monday.

Police say the boy, who would have turned one year old next week, was placed in the tub along with his 2-year-old sister for a bath by the children's father, 27-year-old Sean St. Amand. The father then left the room, according to a news release from the Maine State Police.

When he returned, the boy, also named Sean St. Amand, was unresponsive.

The incident took place at an apartment at 125 Pierce Street in Lewiston. The boy's mother, 28-year-old Jennifer Everett, was also in the apartment at the time, but was taking a nap, police said.

The boy was pronounced dead on arrival at Central Maine Medical Center.

An autopsy is being performed today.