A manhunt is on for the person who shot five people in a rural Pennsylvania farmhouse over the weekend, killing one adult and one 2-year-old boy.

It happened in Douglass Township, about 40 miles northwest of Philadelphia.

Young Gergory Erdmann, just 2-years-old, was shot in the head and killed, as was 43-year-old Joseph Shay, who lived in both New York City and Massachusetts.

Three other people were also shot in the head at close range, and remain in critical condition. They include 58-year-old Monica Shay, an associate professor at the Pratt Institute, Paul Shay, her 64-year-old husband, who owned a plumbing business in Brooklyn.

Also shot was Kathryn Erdmann, the 37-year-old mother of the toddler who was killed, who is from Massachusetts.

The shootings were reported around 10:30 p.m. on Saturday night when one of the victims called 911.

According to published reports, 43-year-old Joseph Shay had a criminal history in New York and New Jersey.

In 1992, he was sentenced in Atlantic County for drug dealing and was relased in 1998. He was also recently put behind bars in New York for grand larceny and was released about a year ago.

It has been reported that Monica Shay bought the farmhouse from her mother, and that she and her husband Paul often went there on weekends.

Joseph Shay was Paul's nephew, and according to one account, Paul was trying to help his relative by allowing Joseph to work with him in his Brooklyn-based plumbing business.

All five people were shot at close range, in the head. Neighbors say the area was quiet, with only a handful of houses on the dirt road where the shootings took place.

Investigators are still looking for the killer.