Well, people have been shot with far less obvious things on their hands mistaken (or "mistaken") for guns.

Besides, what phone camera has a light on it that's visible?

None that I can think of in day/noon/afternoon time. Some have a focus assist light and/or flash at night time -- but taking out of one's pockets and pointing a small object at a US policeman at nighttime, and especially in an aggressive scenario as the one we're discussing, that I would advise even less.