State officials are investigating whether a veterinarian used a gun to euthanize a racehorse at Philadelphia Park, a possible violation of track rules and racing-industry standards.

The probe involves Thomas J. Lurito, a track veterinarian. According to a report in the Daily Racing Form, the injured filly, 4-year-old Rich and Mean, was allegedly shot in her stall about two weeks ago, according to Ralph Riviezzo, her trainer.

"I didn't know how they were going to euthanize her," Riviezzo told the Daily Racing Form on Tuesday. "I was away. I got a phone call the next day that said that they put her down that way. One might argue how humane that is, but I will not get into that argument."

Rich and Mean, sired by Distinctive Pro, injured her knee May 24, finishing eighth of nine in a maiden claiming race. Rich and Mean had raced six times and had failed to hit the board each time.

Philadelphia Park prohibits weapons unless someone is permitted by the Pennsylvania Racing Commission to carry one. Racehorses are typically put down with an overdose of barbiturates, and guns are often prohibited on and around tracks, experts said.

"Frankly, I'm a little taken aback. It's just not the way it's done," said veterinarian Rick Arthur, the equine medical director to the California Horse Racing Board.

Lurito, a Philadelphia Park employee, has been licensed with the Racing Commission since 1995.

The commission, track officials and Bensalem police are investigating aspects of the alleged shooting, which reportedly involved a .22-caliber handgun, said Chris Ryder, spokesman for the Racing Commission.

Gunshots can be a humane way to put down animals, but the practice is no longer done at U.S. racetracks, Arthur said.