Be aware of this...scammer?

I don't want to make any hasty decision but I think a guy named mishelxz3021 (steamrep) tried to scam me...I don't have any proof that's why I don't want to mark him as a scammer, I just want to make you aware of this guy...

In short, he added me to friends list and he couldn't explain how he managed to find me (he had no steamtrades account). He offered me his L.A. Noire: The Complete Edition (KEY) for my Sniper Ghost Warrior Gold Edition (GIFT) and then I've become really suspicious. When I agreed and told him that he need to go first, he told me he got scammed a number of times and that I have to go first. I didn't wanted to and he became very angry and started to insult me. And that's the end of my story, I've removed him from my friends list.

All in all, I just wanted to make you aware of this guy.

Cheers :)

P.S.: I'm sorry for any mistakes in my english :)