It depends on who the victim is..
I probably say yes though. And I think that's the only moral choice. You could use the money to save millions of people. Basically, the question could be rephrased to say "Why you kill the millions of people, or kill just one person?" I think the answer is much more clear there.
If you could choose who to kill, then the answer is even easier. I would kill the oldest, sickest person in the world with the lowest probability of contributing to the planet. But even if its random, I would still do it. Statistically, two random people are more likely to help the Earth and society than one random person. And millions of people are virtually guaranteed to.
However, if the victim is chosen for me, then it would depend on what she/he does.
But of course this is all easy to say now. If presented with the question in real life, I might not be able to do it.