Their 30,000 number is basically correct. What they fail to mention is that on average 55% of those deaths are suicides. They leave that part out in order to give the impression that we live in the Wild West.
And many of the remainder are criminals killing other criminals. Justifiable homicides are also included in the number. And also deranged people killing their estranged spouses, because the latter couldn’t get a gun due to gun control laws (which the 30,000/year statistic is designed to support) are also included in the total.