The joint in your hand intrigues Leon, your best friend. As you're both police officer he's a bit shocked that you smoke, especially weed.

But when you asked him if he'd ever smoked in his life and if he wanted to smoke, he wanted to impress you.

"Sure, who do you think I am?! I'm a pro!"

As soon as you gave him the joint and he took it, he stopped coughing because the smoke was stinging his throat, he wanted to be 'cool' , to impress you.