The databases are not linked at a national level which is why the Vegas shooter was able to amass an arsenal. He was not mentally ill like you said. He was intelligent and knew how to get around whatever checks are in place. I agree the mental health check would have made no difference here. But he did buy over 40 guns, most of which were purchased this year from different states. Do you believe buying this many guns in such a short time should have warranted further investigation?
Also what solutions, if any, would you propose to fix the mass shooting problem in America?
How about for starters a database of people acquiring an arsenal of guns and ammo in a short time frame. Database for additional mental health checks. The problem of mass shootings is a mental health issue, no? Are you OK with lunatics obtaining large amounts of guns and ammo in a short amount of time?
Unfortunately there are no mind readers in the real world so laws are not written based on who is a law abiding citizen and who is not. In fact we are all law abiding citizens until we commit a crime so your argument about infringing upon the law abiding is irrelevant.
The Vegas shooter bought all his firearms legally and he was a good law abiding citizen until he murdered 50 people. Are we supposed to be to read minds and know if his intentions were to commit mass murder or be a law abiding citizen?
The fact remains that noone ever said they were taking away the right to own firearms as allowed under the constitution. We do obviously need more restrictions to prevent these mass murders from becoming so common place. If you are law abiding then additional checks should not be of concern.