That's a little harsh I think. Yobs are more likely to be rebellious and perhaps did not think this was an air ambulance operating at night. To them it would more likely appear to be a police helicopter (flir on the nose) and so an opportunity to get their own back.
Murderers? I don't think so.
Huh? It's ok to shine lasers at any aircraft as long as it isn't an Air Ambulance?