From the article, someone called 911. Presumably personnel from the US consulate, but they should have used their discretion when a professional photographer explained they were waiting for the correct lighting for their photo. That’s perfectly reasonable.

He wasn’t taking pictures in the windows of the consulate or loitering, which explicitly requires there to be “no purpose” to being there, which he clearly demonstrated.

I’m not a lawyer, but I don’t believe the police have the right to demand ID when you’re not suspected of breaking any laws, either.