Cut the cookie dough into 12 equal-sized slices and place onto a sheet tray lined with parchment. Bake according to package directions. Remove from oven and let cool.
Once the cookies are cool, frost them with vanilla frosting. Set frosted cookies on a sheet of parchment on top of the countertop.
In a small bowl, whisk the confectioner’s sugar with 2 tablespoons of water. Add a few dots of red food coloring gel until the mixture is red as blood. Dip a pastry brush or tines of a fork into the red mixture and splatter the red icing all over the cookies to look like blood splatters. Let sit to harden.
To serve, dip a knife into the red icing and place alongside the cookies on a serving platter.