Forest Raven predation

In April 1993 there was a low tide on the Carlton River near Hobart and I
was watching with binoculars some Silver Gulls on an exposed area of sand.
There were two Forest Ravens standing quietly with them.  Suddenly there was
a squawk and a Forest Raven jumped on the back of a Silver Gull and sank its
beak into the gull's neck.  The gull flapped a bit but could do nothing, and
was dead in a minute or two from vicious pecking to the neck and head.  Once
the gull was dead the second raven moved in, and in less than 10 mins. the
gull had been pulled to pieces, and only the wings remained to be washed
away by the quickly rising tide.  
The attitude of the other gulls was interesting.  They did not want to know
about it.  They were within a few feet of the whole thing, and they ignored
it or turned their back on it.