These family of spells - the "freezer family: - are to put a person or a situation "on ice," to slow things down or prevent something from happening. These are not death spells, although you could certainly make the argument that they're a type of curse. I can almost guarantee that you won't be able to kill someone using a freezer spell.
They're talking about one of the spells on this site. If someone actually killed someone useing that spell which I doubt, they'd provably keep silent. Don't try it. It probably won't work. While cursing is common, it's very rare for someone to kill another useing magic and alot harder than you think. The human soul naturally wants to stay alive and it will fight.