...only the GOP is trying to stop murderers from coming into the United States. It is a shame that Democrats support this kind of thing. Please stop making up falsehoods about the GOP.
As far as effective measures, I assume you mean gun confiscation. That would require an Article V Amendment to the US Constitution. Obviously that won't happen. If it did, there would be a revolution. Law abiding citizens just won't give up their right to defend their families. The only way to solve this problem is to keep the border closed, expel criminals, put US citizen criminals in jail (not release them to prey upon the public as the Dems like to do), and re-open the insane asylums and provide mental healthcare to people once again (rather than encouraging their mental illness, and/or leaving them to fend for themselves on the streets, both strategies that the Democrats promote).