SCOTUSblog has the scoop. David Savage offers some context.
UPDATE: I personally don’t see very much in this: Recall that one of Justice Alito’s very first votes was a vote against lifting a stay of an execution when the other conservative Justices voted to lift the stay. It makes sense that a new Justice with little experience in capital cases would be extra cautious, so it’s hard to read much into this, I think.