From the article:
“Northington said Target officials told him that he had violated procedure by not filling out the proper paperwork before contacting the police, though he said his office had operated the same way for years. He said he also was told that he had been insubordinate for not seeking approval before calling police, though he said the standard practice was for him to act as needed.”
If the store has a policy in place I’m afraid that will overrule “standard practice”. He may not have a leg to stand on.
I would imagine a decent lawyer could sway a jury with questions regarding “why was it so vitally important now, out of nowhere?”