Police are investigating whether a firearms officer accidentally shot a bullet into an empty office while hunting an escaped bull.
The bull had escaped from the cattle market in the town centre
Officers destroyed the animal which had escaped from Mold cattle market in Flintshire on Friday afternoon.
Later that day the boss of a security firm found a bullet had broken the window of the unoccupied room.
North Wales Police said the incident had been referred to the Independent Police Complaints Commission (IPCC).
The bull was shot dead by fire arms officers in a field next to AGS Security Systems Ltd in Denbigh Road in the town.
Managing director Jonathan Turner said he had been in a health and safety training meeting with his engineers when they heard an "enormous bang".
They got up and looked out as they heard a couple more shots, and saw that the animal had been shot.
"It was an enormous bang. I thought something had hit the building, like a firework or something," he said.
But Mr Turner said it was only later when he was locking up the premises that he realised what had happened.
"The office next door to the meeting is unoccupied at present and is being renovated," he said.
"When I went in there I saw that the window was broken.
"The bullet had gone through the window, across the room and hit the wall the other side.
"If it had happened in the next door room then there would have been someone there, and could have been seriously hurt."
North Wales Police confirmed officers had been called to an incident involving an escaped bull, which "appeared to be causing a danger to the public".
A spokesman said the bull had been "humanely destroyed" and no-one was injured.
The spokesman added: "The incident was voluntarily referred to the IPCC, as it appears that a round that was discharged may have broken a window at nearby commercial premises.
"The matter is being properly investigated and as the investigation is ongoing it would be inappropriate to comment further at this stage."