As I see it, there are two schools of thought emerging strongly off the back of the shooting
- Guns are bad, and the less guns that are out there the less these events will occur, thus banning assault weapons will prevent violence - Certainly this is persuasive. Most of Europe has banned the majority of firearms, certainly assault weapons do not exist in public circulation, the availability of handguns varies but again, tends toward either outright bans or low incidence
- Violence is the result of something cultural and guns in and of themselves do not have a significant role - As has been noted, plenty of societies allow ownership of firearms and yet massacres of this sort (individuals losing control and killing for non rational reasons) seem to largely be limited to the USA. Switzerland, Finland, Sweden, Norway and France all have significant numbers of guns in society, and yet do not suffer from sudden surges of violence.
Working to eliminate and criminalise the ownership of assault weapons could only have a positive impact on gun crime. If owning and moving this type of weapon is a criminal offence then opportunities exist to arrest criminals long before they get used in further crimes. The marginal costs rise, both practical costs ($ and £), but also the moral cost, which would push the average citizen out of the market in many cases.
That said, there is something unique to American culture which needs to be addressed too. There have been some good discussions about how to rethink mental health treatment to help ensure that individuals who are going down a dark path are picked up earlier and their violence is never allowed to boil over. There is a challenge here however, particularly in the USA, since in order to have a mental health system capable of addressing these challenges you would need to build a system where costs for mental health care are much lower for the individual. In order to do that some form of socialised health care would likely be needed.
The point is however, that these are not partisan issues, and making one issue "Democrat" and the other "Republican" is to needlessly confine them to a particular voting group. If both solutions have merit the goal should be to find ways to implement both in a meaningful way over time, and to assess the impact that it has. I worry that as it stands the issue is lurching towards deadlock.