What if I found a big Bitcoin address?

Let’s assume I randomly generate private keys and just happen to get the same key as some 1000 BTC whale and getting access to them (I know the odds). Then I transfer them to another address, and go to any exchange to cash out. What would happen? Would I get arrested for theft? Would the officials assume this is illegal money, as I cannot explain where I got them? What about taxes?

Little mind game, what do you think? Of course it’s just hypothetical, as the chance of actually brute forcing such an address is like nonexistent

Edit: Guys I know how statistically impossible it is, I even calculated it myself in the comments (and compared it to billion monkeys each with a billion typewriters). I was just wondering if it would be legal to „steal“ the coins. I could also just steal the private key backup in the physical world, and then steal the coins. Same thing