The 'Wedding Crashers' star believes the people who carry out the shootings specifically target places of education as they know there are no guns there.
He said: "Take mass shootings. They’ve only happened in places that don’t allow guns. These people are sick in the head and are going to kill innocent people. They are looking to slaughter defenseless human beings ...
"In all of our schools it is illegal to have guns on campus, so again and again these guys go and shoot up these ... schools because they know there are no guns there. They are monsters killing six-year-olds."
The 45-year-old actor - who says he supports "having a gun in public, full stop" - also insisted banning firearms would not remove criminality in its entirety.
He added to GQ magazine: "You think the politicians that run my country and your country don’t have guns in the schools their kids go to? They do.
"And we should be allowed the same rights. Banning guns is like banning forks in an attempt to stop making people fat. Taking away guns, drugs, booze ... It won’t rid the world of criminality."