Law enforcement authorities have arrested two men and a 13-year-old boy in connection with the shooting of a pregnant mare near Sundre, Alberta, last year.

Jason Nixon, 29, and Earl Anderson, 40, both from the Sundre area, have been charged with killing cattle and careless use of a firearm. The 13-year old cannot be identified under Canada's Young Offender's Act. According to a statement from the Royal Canadian Mounted Police, charges are also pending against a 35-year-old from the Calgary area.

Doreen Henderson, secretary and treasurer of the Wild Horses of Alberta Society, said she is happy arrests have been made, but believes there is more than one group of people responsible for the shootings. Since 2002, more than 30 wild horses have been shot in the area.

"Unfortunately, there are some people who think of the horses as a nuisance," she said. "I don't know that the shootings will ever stop completely, but this is a huge deterrent. Now people will think twice, because there's the possibility they might get caught, whereas before, no one was ever charged."

A Crime Stoppers video and $25,000 reward had "influence in moving this case forward," said Sgt. Patrick Webb, media relations officer for the Calgary RCMP, who expects the reward will be distributed to the tipsters that aided the investigation.

"We're further ahead than we've ever been in the past in this investigation and there very well might be more arrests and more charges. This is only one incident, we're still investigating the others," he said.

Nixon and Anderson are set to appear in provincial court