I watched it again last night, and you're right - they realised it wasn't just the vamps but the Alpha too, hence the panic stations!

And the scene of Sam shooting the Alpha was so cool, with the hole right through his head! But I'm sorry they killed him off.

" I felt there was a strong nod back to Bloodlust in the Ketch/Dean bond. Dean was drawn to Ketch in the same way as he was initially to Gordon, because he claimed a kinship and understanding of Dean's dark side but, as in Bloodlust, Dean drew the line at wanton sadism."

So right - Dean will kill because he has to, and gets a rush from it, but he's not a sadist and I loved that Dean stopped Ketch from hurting the vamp - he's a nasty bully.