The fact that Zimmerman wanted to have Martin questioned, and that he (Zimmerman) was in fact carrying a gun, and that he was directing himself toward Martin, would strongly suggest that Martin was made aware of the gun. Between the possibility of coming aware of it through some other means, or coming aware of it due to Zimmerman purposefully making him aware of it, it is extremely likely that he became aware of the existence of that gun.
You can take this in further, to make it become almost a certain conclusion that Martin became aware of the gun.
But a jury may choose to reject everything except Zimmerman's words, if a route is left open toward doing that.