The 'pid' of subprocess is changing and i can't terminate subprocess

I need to write a programm that opens a windows explorer on the folder that the current script is on, every time user inputs 's'. And every time user inputs 'e' i need to close active windows exlplorer process.

this is my code:

import msvcrt
import os
import subprocess

input_char = ""
ALL_PROCESSES = []
file_directory = os.getcwd()

while(input_char != b'~'):
    input_char = msvcrt.getch()

    match input_char:
        case b's':
            #OPEN EXPLORER
            proc = subprocess.Popen(f'explorer "{file_directory}"')
            ALL_PROCESSES.append(proc)
            continue
        case b'e':
            #CLOSE ACTIVE PROCESS
            subprocess.call(['taskkill', '/F', '/T', '/PID', str(ALL_PROCESSES[-1].pid)])
            ALL_PROCESSES.pop()
            continue
else:
    print("Finished")
    #close explorer

Every time user enters 's' i open internet exloprer and save subprocess object to array. And everytime user enters 'e' i try to taskkill last opened process by its pid and i get next error:

ERROR: The process "7140" not found.

Why does the saved in array process changes its pid over time, and how can i keep track of it so i can successfully close it?