Where/How do you buy guns?

[[PWM] Sir. Paulord]

I'm not too advanced in the game, but I already did the mission where you go to a guy that sells guns and you have to shoot some bottles, so after that, I thought I should be able to buy guns and ammo. But I just went to that place (which is the only gun shop that I can see in the map) and there was noone there, I wasn't able to buy guns. So, do I need to come at a specific time of the day? Do I need to buy them somewhere else? Or isn't it possible to buy guns at this point of my game?

[Agarillobob]

he does not sell guns, he gives you a gun for free always
You can buy weapons from the ammunation shops all across San Andres, they open after the mission "Doberman" iirc