I will describe my walkthrough.
First, I entered mansion, went to the basement and retrieved the key. Then I headed to the room that I am supposed to assassinate someone. I killed him, then I went to restroom and disguised as a guard. After that I killed a guard bot with m4a1-sbesides the VIP. The kill was taken place near the pool, with one-tap at the head. After the kill, another guard bot soon reached me. Now here is the thing: As the bot was going to shoot me, and I was going to shoot it as well, THE GAME CRASHED!!!
Perhaps, you can re-trigger this crash if you followed my steps. Duly note that I didn't make any loud footsteps.