i know how but i can't reveal it easily, so imma do it on a riddle
in order for this to work you need a firearm.
go to the mini house and choose the option yes
leave this establishment
now go to the HeadQuarters
solve the puzzles below to know where to go.
Move S - 1, J - 1, M - 3, J-2, X - 4
Choose the option to attack
choose 1 - 4=N
see HIM, kill HIM
you get your ending, hope you solve the riddle