Is this the culprit?

Woke this morning to see a heron rising from our pond with something in its mouth.
 
 
Surely not?
 
A quick inspection revealed all eight fish had gone.
 
We had thought this pond was totally inaccessible to heron’s because of the high laurel hedge and it did have great difficulty getting out.
 
 
M had looked after the fish all winter and only yesterday did he partially remove the top protective covering to allow the water lilies to come through. 
 
Worse, the pond heater was on overnight and the fish loved to cuddle around it for warmth. So they were sitting targets.
 
Is this the culprit? He hangs out under the bridge in Bridge of Allan.
 
   
Only a few days ago I blipped the fish.