tkinter: Spawn a new process with multiprocessing which runs the TK mainloop

Question

I'm trying to spawn an "unusual" child process: My main process runs in the command-line or an embedded environment, which spawns a new process that runs a Tkinter GUI. But this crashes python (3.6 on Mac) right away.

import multiprocessing as mp
import tkinter as TK


def RunGUI():
    root = TK.Tk()
    root.title('Hello Child GUI')
    root.geometry('{}x{}+0+0'.format(768, 768))
    root.resizable(width=False, height=False)
    root.attributes('-topmost', True)
    root.mainloop() 

job = []
p = mp.Process(target=RunGUI)
job.append(p)
p.start()

Is it that Tkinter does not support this usage pattern or am I doing something wrong?

UPDATE

The error message I got is like this:

**Python quit unexpectedly**

Click Reopen to open the application again. Click Report to see more detailed information and send a report to Apple.