The cops were on their way and they would be there in minutes. That’s a policeman’s job. He has no authority. They wanted him to meet them at the gate so they can check things out with a marked policeman. There was no immediate crime or crisis. only in Zimmerman’s warped imagination.
A witness stated that Zimmerman was on his way back to his truck when Trayvon jumped him.
I'd say that is really damn "immediate".