Lets use the nails as the cores and use the snow to get the blood of the one guy.
Yeah, let's do that and merely puppet them so we can move them somewhere safe. Not necessarily back to the library, maybe Esme knows of a safehouse or abandoned building that's closer.
Once there we can perform surgery to get to their hearts.
You ask Esme about necromantic bodies rotting. She knits her brows and thinks for a moment.
"I think that puppets rot, but that if they have a spirit in them they will stay mostly the same? Or at least they won't rot but they might mummify or generally change. Alexander used to keep his in a freezer when he wasn't using them, to keep them fresh."
You ask about a safe place nearby, somewhere you can take these bodies to work on them more effectively and without the fear of having someone happen upon you elbow deep in a police man's chest cavity.
"We probably shouldn't bring them to the library at all. Too much of a risk. We could hide the bodies in one of these warehouses but there's a good chance they'll be searched after the men are reported missing..."
She pulls a street map out of her pocket and holds it for a moment, eyes closed. You see things rapidly slither across her skin and up her sleeve. You start working on the bodies in the meantime. You have piecewise insert nails into each man's chest, pushing it right into the sternum until the head is flush with the skin. One by one you spill a little blood and connect the anima to the bodies. Having 3 bodies puppeted at the same time makes you feel distracted or foggy. You can feel them leeching off your mind to understand things; even as simple as they are, its still like trying to do 4 things at once. Luckily the mana drain from the reanimation is pretty slight, you only feel a bit tired. You have piecewise finish them up by hiding their injuries while you talk with Esme.
"There's a few options" She says, putting the map away. "About four blocks away is a warehouse that we control; its one of the ways we get things into and out of the city. Its ours so we know its safe for the moment but it might be within the radius that they'll look for these guys. Beyond that there's a meat packing plant maybe two miles that way," She indicates a direction to the east, "Not ours but it should have refrigeration and we might be able to effectively hide them. But, if anyone finds them- or us- its gonna cause a stir. Last place is a mortuary. About 3 miles north. Good place to hide bodies, I would assume, but its not under our control and it would mean having to march these guys through city streets."