Reddit mentions of Magic in the Shadows (Shadowrun)

Actually, in previous editions, there were rules for a sort of necromancy. Corps cadavres are created by magicians, typically houngans or mambos (voodoo practitioners), casting a spell on a dead body. It's active for a while, but has no real will of its own or longevity. They could also create was was called a loa zombie by ritually preparing a corpse to be inhabited by either a free or ally spirit, but in that case the spirit is the one in charge of the zombie, although it's capable of much greater autonomy, and is significantly buffed by how powerful the spirit is.

Awakenings: New Magic in 2057 discusses the rules in depth (and has a lot of the best in character explanations and discussions of magic ever published in Shadowrun). The 3rd edition magic sourcebook, Magic in the Shadows also covered the voodoo rules, but in much less depth.

Those books are in the second and third edition respectively, so you'd have to adapt them to new editions, but the backstory is there to be used.