The money suitcase dilemma

Hello,
Today we were asked in a large group about the following dilemma:
You and another person are hanging out in the park, when suddenly a billionaire approaches and decides to do a good deed. He offers you both a suitcase worth 10 million shekels.
The condition is this: You must arrange the division of the reward between the two within a minute. If they don’t agree on the amount, no one will get anything.
 
The stranger comes to you and says: “No matter what you choose, I tell him I’ll take the entire amount except for 10,000 shekels, which I’ll leave for you.”
No matter what, he is not convinced.
And the question is this: Will you take the amount or will you choose a situation where no one takes anything?
 
I replied that I would choose money, and that’s because I am not motivated by feelings of revenge and I don’t care about the happiness of others.
The others attacked me and said: If he took such a large sum, he must be a selfish person, and I don’t want his best interests at heart. And it would hurt my ego too.
 
Is there a moral issue in the dilemma?
Would taking the money be an unethical act on my part? Since I am cooperating with selfish actions.