Oh hun I am so sorry hear this...
It happend to us about 3 years ago....it was to a very old gentle cat (but his owners didn't give two hoots about him he was out in ALL weathers)..
He spent most of his time here with us...but would never come in..
He was killed by a pit bull X staffie...we even knew where it lived...they just left him to die on his own after being torn to bits by this demon dog.
Two weeks later further down in the next road...the same people set the dogs on another cat..again an elderly cat..
We still miss him..poor Minn...such a horrid way to die..
It took all my strenght to stop Simon going around to their house to do the same to them...
The dogs have since disapeared thankfully....we think they might have been involved in dog fighting...as they always looked battered...and ready to attack anything in sight..
One of them even knocked Simon almost over...as they were never on leads.
I am so sorry for your friend...I really feel for her...please give her our best wishes and thoughts..
We have just lost our old Barney a few weeks ago..so I know how she must be feeling...
Love Annette & Simonxxx