Learn Portuguese (Portugal): O ladrão deu um tiro para o ar.

In Portuguese, the verb dar (to give) is highly versatile and forms many expressions. To say to fire a shot or to shoot, the standard phrasing is dar um tiro. You could also use the verb disparar directly (O ladrão disparou...), but dar um tiro is extremely natural and common.

Could I say no ar instead of para o ar to mean in the air?

Using para o ar specifically highlights the direction the gun was pointed (upwards, toward the sky), directly translating to into the air. If you used no ar, it would imply the location where the action happened, making it sound like the thief was physically floating in the air when he fired the gun.

Is there a verb related to the noun tiro (shot)?

Yes, the verb is atirar, which means to shoot or to throw. Instead of using dar um tiro, you could simply say O ladrão atirou para o ar (The thief shot into the air), which conveys the exact same meaning without needing the noun.

What is the plural of ladrão?