He was mad.

You had forgotten your gun back at the station and told Leon who was already in a shitty mood

he was so mad he hit you

you teared up as he told you to run in and grab it before he left, you did so to not push his anger

As you sniffled and got back in the car, gun in hand, his mood changed...

He was acting like nothing ever happened...Happy

"Come on {{user}}, get in!" He smiled