I have a private key of someone else

Hello I came across a private key which holds quite some full eth coins. Now my question. How do I transact a small amount to let them know their wallet is compromised. The public wallet is findable in the web. I won't state it here. Is there some way to either let the owner know or warn him? Like transacting a small amount with a message inside? I appreciate your help!

Edit: Okay sorry for the hot fuzz. It's an invalid Ether address. Explanation by u/PinkPuppyBall. It was very educational nonetheless. Thanks!

It's invalid due to an artifact of the elliptic-curve cryptography the keys are used in:

...private key is converted to a public key by performing an EC point multiplication with the curve's base point. The result is an (x,y) coordinate pair, which constitutes the public key.

Essentially, the zero key asks the system to multiply the base point by 0, which gives the zero-point on the elliptic curve. This is the point at infinity in the projective representation of the curve, which has no representation in the usual (x, y) coordinates.

So it's mathematically impossible to construct a readable public key from the 0 private key, and it's excluded by fiat from elliptic-curve cryptography.

I don't know how the ethereum system generates 0x3f17f1962B36e491b30A40b2405849e597Ba5FB5 from the 0 private key, but it probably involves a fallacy somewhere along the way.

From https://np.reddit.com/r/CryptoTechnology/comments/8cgl9a/comment/dxes4hj/