LOWELL, Ind. (CBS) — Police in northwest Indiana are hoping a reward will lead them to the person who killed a racehorse as it grazed last week.

The Humane Society of the United States is putting up the $2,500 reward for information that will lead to the arrest and conviction of Lady May Z’s killer.

Lake County (Ind.) Sheriff’s Police have said that the horse was killed May 29 as it grazed in its pen. Owners Carl and Heidi Geib found the racehorse dead a short time later.

LISTEN: WBBM Newsradio’s Bob Roberts reports

The eight-year-old standard-bred filly was scheduled to appear at Balmoral Park Racetrack the next day.

“It takes a truly callous person to shoot a gentle horse point-blank as she was grazing in her pen,” said Anne Sterling, Indiana state director for the society, who called the shooting “tragic.”

Police at first thought the horse was shot between the eyes, but now say they believe a captive bolt gun was used in the shooting — a device that is used in processing plants to stun and kill livestock about to be slaughtered.

A pathologist said the gun inflicted blunt force trauma to the brain.

Watch & Listen LIVE