Installing kill switch. Need help.

I want to install a kill switch in my 2000 crown vic police interceptor. The problem is I took off the ignition casing under the steering wheel and I see 5 small wires running away from the ignition(white, orange/white, black, purple and blue). There is one thick black/purple wire running to the ignition and another black wire running to the ignition too.

Which wire do I cut to connect the kill switch? I want to connect to starter wire. Just want to kill the starter and nothing else.