These things are easily said, but we don't actually know what went on.
Woody was two-and-a-half and was off-lead, and recalling, every day. Sometimes dogs get distracted, or panicked, or caught up on something. We don't know why he didn't recall, or why he was shot.
He wasn't being walked on the day of the shoot but the day before, it's not as if he was deliberately put at risk, and the shoot were advised that day that he was missing in the area.
His owners did everything they could to find him but were not allowed onto the land of the day of the shoot. It seems somebody got to hi