Can we stop letting low IQ individuals buy weapons? Would you place a rifle in Trump's hand and stick around to see what happens?

Life in prison or the death sentence - lethal injection, electric chair, gas chamber, etc., has never been a deterrent or prevented a person with an average IQ or above from committing murder. I don't know or can I predict what trump would do with a 'gun', he may already have one. I'm not a supporter or a member of his cult base believers.