Tbh, even if you have a gun, your odds are not 100%. You're firing at essentially a biological tank, small caliber fire might cause pain and eventually kill a polar bear with non-vital shots, but it's not going to stop one barreling down on you.

Realistically, you need to be a decent enough marksmen to aim for a vital point, all while making your will saves because a giant monster is charging you. I'm pretty sure most humans are still fucked.