A small group of A's and B's are plotting to raid to the C block and work their way into D block. They will release nearly all C's from their cells, and a select few of D's (due to the high risk one of them could indiscriminately kill everyone.) Winston's ability of immortality causes him to a victim of organ removal. During these organ removal surgeries, accidents happen. Surgical tools are sometimes misplaced in his body. Using a scalpel (accidentally forgotten in his body), he'll have an assistant cut off his foot, removing his anklet. At this point, if the anklets double as life monitors, then security will investigate.
He'll kill a guard and steal his weapon. If shooting off anklets is possible, he'd use all the ammo in the gun to release the most useful inmates in blocks A+B. He knows of a teleporting inmate (Block D) and plans on using him.
His own escape isn't what he wants though.