Withdrawing large amount without proof of acquisition

When I was a minor back in 2015, my old friend’s big brother convinced me to invest in Bitcoin. He said the price will go to ten thousand. As a naive kid I believed him. Since I was too young to buy any myself, I paid him around $3000 cash to make the purchases for me. That was money from years of red pocket. In hindsight, it was a very stupid but lucky investment. He kept custody till 2021 where he transferred the money in my hardware wallet. I kept the BTC ever since then.

I now need to cash out close to a million dollars, but I lost contact with the person who initially purchased the BTC for me because I believe they moved overseas (he should be filthy rich now).

I have no way to document proof of the source other than the BTC landing into my wallet in 2021.

How should I declare my ACB? Is it best I work with a CPA or tax lawyer?

At this point I’m ready for an audit, but will I be in trouble or criminally investigated for because I suddenly deposit so much money into my bank?

Does anyone have a similar story? Or has anyone withdrawn large sums without proof of purchase?

I am in Canada btw.

Thanks.

EDIT: Thanks everyone for your response. I've answered many DM's for fun to fuck around with the scammers lol. Like many suggested, I'll reach out to a tax lawyer first, then a crypto CPA. I'm not moving to another country bruh - I'll handle all of this LEGALLY! I like being able to sleep at night.