Well I am of the opinion that there would be a standard procedure for this type of threat. I am of the opinion that once this aircraft landed the Captain should follow instructions given from the ground.
I seems this Captain followed the regulations and followed instructions given.
One that did not and ordered an evacuation after being told to wait for further instructions could be accountable for personal injury's that would follow. These are of the type that should not be blaming the police for taking too long - but they are!