Why did luhrmann have mercutio throw down his gun before encountering Tybalt?

I looked up this question because I had the same thought rewatching this film today. It's interesting that in Shakespeare's play, Mercutio clearly wants to pick a fight from the moment the Capulets walk in, baiting Tybalt - who initially doesn't bite - and eventually outright challenging him to the duel in which he is killed. In the play, he does this because he's disgusted with what he sees as Romeo's 'cowardly' response to Tybalt's challenge; however, Luhrmann's film makes a big change here. In the film, Tybalt and his thugs are literally beating Romeo up (there is no indication that this happens in the play), and Mercutio's motivation is clearly to save him from the beating. So why throw down his gun first? It's not entirely clear, but it seems to me that Luhrmann's version of Mercutio, unlike Shakespeare's, does not intend for this to be a fight to the death. Instead, he grabs a makeshift club and jumps into the fight in order to beat Tybalt back off Romeo. There may be other interpretations, but I can't see how else to read this strange and very deliberate piece of adaptation. It certainly makes his death more tragic - he's killed defending Romeo's life, whereas in the play, it seems all he was defending was some sense of honur - his own or Romeo's, it's hard to tell.