LA CROSSE, Wis. -

La Crosse Police are investigating a shooting in downtown La Crosse that leaves two dead.

Paul Petras, 56, and his son AJ Petras, 19, were shot to death in May's Photo store, 425 Main Street, on Saturday.

Petras owned May's Photo and his son AJ worked there. Petras was a 2011 graduate of Aquinas High School and was known by friends as an avid snowboarder.

Police tell News 8 the double homicide was discovered about 5:00 p.m., but they think the deaths happened about 2:00 p.m. That's around the store's closing time.

News 8 was also told a photography class was held Saturday afternoon leading up to the store's closing.

"When I got the call, it was really gut wrenching," said Capt. Robert Lawrence, with the La Crosse Police Department.

"It was something that really took me back that we have another homicide that we are investigating," he added.

The Department of Criminal Investigation is sending a team to La Crosse to help with the investigation.

According to newspaper archives, Paul Petras ran May's Photo started by his father. They formerly had a store in Winona, Minn.

Police said they do not know whether Paul and AJ Petras were targeted, or if the shooting was random. But they do say there is no additional known or imminent threat to public safety.

They're asking anyone who attended the May's Photo class ending at about 2:00 p.m. Saturday to contact law enforcement immediately.

Police would also like to talk to anyone who was in the area of the 400 block of Main Street between 1:30 and 5:15 p.m. Saturday who saw anything unusual.

You can contact the department at 608-785-5962.

"It's imperative for the community to let us know anything (suspicious) that they saw," said Lawrence.