There were multiple actions taken by the Court today on this case. I believe at least four orders of some kind were issued. They'll be entered at the Supreme Court website by tomorrow.
A lot of people are saying that Alito voted this way because he was unfamiliar with the case. If so, then he should have recused himself as he did in the Rutherford actions (also related to the death penalty).
A more likely explanation is that Alito's very mixed record on capital punishment in the lower courts is not a fluke, and that he actually does side with the merits of letting the inmate's case go forward.
Or maybe he will emerge as an opponent of capital punishment. After all, wasn't the implicit notion that he would rule according to his Catholic faith thought to be a positive? The Roman Catholic Church is adamantly opposed to capital punishment.
Roberts, Scalia, and Thomas are all practicing Catholic so your dumb argument that the Alito Catholicism has effected his judgment on this case is absolutely wrong. The man has been on the court for few hours and he just needed more time to hear the case before ordering the execution of a man, it is a simple as that.