The article says the police later showed the student the photo that triggered the alert. He had a crumpled-up Doritos bag in his pocket. So there was no gun in the photo, just a pocket bulge that the AI thought was a gun... which sounds like a hallucination, not any actual reasonable pattern-matching going on.

But the fact that the police showed the photo does suggest that maybe they did manually review the photo before going out. If that's the case, do wonder how much the AI influenced their own judgment, though. That is, if there was no AI involved, and police were just looking at real-time surveillance footage, would they have made the same call on their own? Possibly not: it feels reasonable to assume that they let the fact of the AI flagging it override their own judgment to some degree.