If I had a 1,500 FPM sink rate going at less than 1,000 AGL, I would seriously consider going around, and definitely would have at the "sink rate" call that close in.
According to the UPS FOM excerpts in the docket, over 1000 fpm sink at 1000 feet AGL (actually above the runway as GlobalNav points out) is a mandatory go around.
Some carriers are required to call 'stable' or 'go around' at 1000 feet, apparently UPS does not do this (yet, anyway - I'd almost bet it will be the new procedure after this crash).