The owners of a State Fair patrol horse on Tuesday were offering a $500 reward for help in finding the person who slashed the horse's throat over the weekend in their pasture in Inver Grove Heights.

Owner Patty Stadt said the 15-year-old quarter horse named Bo had been part of the State Fair's Mounted Patrol for 10 years.

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"He loved it," she told My FOX Twin Cities of Bo's fondness for the work.

Stadt says she and her husband, Richard Stadt, found Bo dead about 5:30 a.m. Saturday in the pasture where he was left to graze overnight with their other horse. Stadt estimates the killer struck sometime after 11 p.m. Friday.

"It was horrible," she said.

The Stadts said Bo was a gentle, even-tempered horse, which ultimately led to his demise.

"He was very trusting," Richard Stadt told My FOX Twin Cities.

Police had no leads or suspects in the case.

The Associated Press contributed to this report.