I would actually argue that convicted felons that have served their time should be allowed to own firearms. Presumably the penal system deals the punishment appropriate with their crime. It is not a life long detriment to inalienable constitutional rights. If we don't trust former prisoners then that's a problem with the penal system itself that should be corrected.

That being said, these types of events will only become more and more common. The government really shouldn't expect to control the proliferation of weapons in the future. However scary that sounds to some, people already have this capability, so it isn't likely to suddenly create chaos.