Why is this wild animal wearing a collar and painted with the word "pet"?

This buck—wearing a collar and emblazoned with the word "pet" in paint—was spotted in rural Missouri, about 35 miles southwest of St. Louis.

"Somebody most likely took that deer out of the wild as a fawn and tried to keep it as a pet and put a collar on it," Missouri Department of Conservation Captain Scott Corley told the Belleville News-Democrat. "We're concerned with the health of the deer. And nowadays since we have issues with chronic wasting disease and other disease issues, [interaction] is not safe for humans and it's not in the best interest of the animal's welfare."