Seeing as it can lead to fatalities to bystanders [1], I would be fine calling it "violent". [EDIT: "potentially violent" being perhaps a better term].
In my opinion, this is why at last gun education would be a good bipartisan way to reduce gun accidents (if not gun crime). If a police dispatcher does not think that firing into the air is serious problem and can kill people, that in itself is a big problem.
I was browsing the ShotSpotter website, and they have a paper that talks specifically about celebratory gunfire. [2]
[1] http://www.bbc.com/news/magazine-14616491
[2] http://www.shotspotter.com/system/content-uploads/MYTHS_abou...