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BUFFALO, N.Y. (AP) — A father of four shot and killed his wife and mother at different locations in New York before killing his father and himself at a shooting range while his children were in school, authorities said Friday.

Sheriff’s deputies responding to the outdoor range in Newstead, northeast of Buffalo, on Thursday found the body of Erik Bergum alongside that of his father, Mark Bergum. Mark Bergum had been shooting at the range when his son arrived and joined in, Erie County officials said at a news conference.

“The son actually started shooting at the range, and then after shooting at the range, went ahead and killed his father,” District Attorney John Flynn said.

The investigation led to the discovery of the bodies of Erik Bergum’s wife, Mary Beth, and his mother, Nancy Bergum, at two separate homes in the town of Clarence, Sheriff John Garcia said.

“Every time I received a call it was gut-wrenching,” Garcia said at a news conference, “when the mother was found dead, when the wife was found dead. Thank God the kids were at school.”

Erik Bergum outlined the killings in a note that was found in his car, indicating he planned the shooting spree, authorities said. The note did not include a motive.

Investigators believe Bergum shot his wife first and then drove to his mother’s house and killed her.

Garcia called it chilling how Erik Bergum, after killing the women, was able to drive to the rural shooting range and join his father in target practice before killing him. Murder-suicides are often crimes of passion, the sheriff said.

“For that to be planned out, we’re thinking that morning, and for him to actually shoot at the shooting range with his rifle and have a great grouping from 100 yards lacks that passion and it’s so calculating,” he said.

Flynn said Mark Bergum had earlier told a witness at the range that his son was coming to join him and the witness moved over to make room.

“There is no indication that the father was aware of what the son had just done,” Flynn said.

Erik Bergum and a partner owned a home theater and home security business, authorities said. Bergum was convicted of misdemeanor insurance fraud related to the business in 2011 and received probation.

Mary Beth Bergum originally was from Maryland. Her father was en route to western New York Friday, Garcia said.