HEBRON, Ind. (CBS) — A northwest Indiana family is trying to come to terms with the sudden and violent death of Michael Pasternak, Jr., who was killed over the weekend in a mysterious shooting while he was mowing a lawn.

Pasternak and his father, Michael Pasternak Sr., operate a Gary lawn care service and were hard at work Saturday.

The younger Pasternak was atop a riding mower, cutting the backyard grass of a Hebron residence as his father looked on. Then, all of a sudden, Michael Jr. was fatally wounded.

His father said he heard a “pop-pop-pop” sound and his son fell over.

“The mower kept going and went through a fence. I rushed over there and shut the mower down because the blades were still going,” Pasternak Sr. told CBS 2’s Mike Parker.

He says he tried to comfort his son as he yelled for neighbors to call 9-1-1.

Sabrina Kasich, who lives nearby, heard the disturbance.

“You could hear the lawn mower going,” she said. “All of a sudden you hear the lawn mower stop and you hear, ‘Help! Help me!’”

The yard abuts farmlands and woods in the distance.  Kasich says she thinks the shots could have come from a hunter. She said residents can hear gunshots, given the openness of the area.

Indiana State Police said there were no leads in the case Monday.