I've said this to Cumore and I will repeat it for everyone here.

I might have killed for my secret. In fact, it might have been the only thing that could have moved me to take an incentive. But the person I would have done it for is dead.

If you think back to the hostage motive, you might remember Rembrandt handing me a note saying everyone I care about has died already. That's your proof, there.