Yes, you do need to explain. And you said it very well here:
"he treated me great when we're alone, but treated me like crap in front of his friends."
He is unable to show that he cares about you in public.
Yes, that's reason to drop this immature, selfish, guy who CARES MORE ABOUT WHAT GUYS THINK OF HIM
than he cares about you.
Find someone more mature. Don't ask about him. And don't care about what he does. Believe me, he's going to try to make you jealous.
Walk away with your head held high.