A Denver Police Department mounted patrol officer has been docked one vacation day after he left his horse tied in a stall for 16 hours without food or water. The horse developed colic and was euthanized.

Denver police internal investigators did not believe Officer Joseph Teeter intentionally ignored his horse, MC Hammer, after a day of patrolling downtown, and veterinarians could not conclude that the illness was a result of being tied for so long, according to a disciplinary letter issued to the officer.

Teeter, who has been with Denver police since 2006, violated a department rule for carelessly leaving MC Hammer tied, said the Dec. 20 disciplinary letter obtained by The Denver Post.

Teeter remains a member of the department’s mounted patrol, said Christine Downs, a Denver police spokeswoman.

“Though not intentional on his part, Officer Teeter’s forgetfulness exposed a live animal to cruel and extreme conditions,” the letter said.

Teeter and MC Hammer patrolled downtown Denver on Sept. 26, when temperatures were in the upper 70s. Upon returning to the mounted patrol barn, Teeter unloaded the horse and tied him to an eyebolt in the stall and removed his saddle, the letter said.

Teeter took the saddle to the tack room, but he became distracted with paperwork and forgot about his horse. Someone else discovered MC Hammer tied in the stall at 6:15 a.m. the next day, the letter said.

The horse was given food and water and first appeared to be “bright, alert and responsive” for several hours. However, the horse began showing signs of pain around noon and he was taken to the Littleton Equine Medical Center.

MC Hammer was evaluated and monitored overnight.

The next morning, the horse was diagnosed with colic and veterinarians determined he would not recover.

“The medical experts who evaluated the horse were unable to conclude that the horse’s condition was caused by being left tied in the stall without food or water for sixteen hours,” the letter said.

MC Hammer was 10. He had been donated to the department in November 2015, Downs said.

The letter said Teeter had taken responsibility for his conduct and had shown genuine remorse.

“The officer feels horrible about this situation,” Downs said. “It was an accident. We love our animal partners.”