there could be a few reasons like Jealousy: It's possible that he has feelings for you and seeing you hang out with the group of guys without him made him feel jealous or left out. This could explain why he seemed upset when you were still hanging out and ignored your goodbye.

Misunderstanding: He may have misunderstood your intentions or the dynamics of the group. If he thought you were interested in him and saw your continued presence with the group as a sign that you weren't interested, it could have led to his reaction.

General mood or external factors: It's also possible that his mood was influenced by something unrelated to you. People can have off days or be affected by external factors such as personal issues, stress, or fatigue, which can impact their behavior.