What is etomidate, how does lethal injection work and what other drugs have been used in executions of death row inmates?

LETHAL injection is the preferred method of execution in the 31 American states that have the death penalty, but the drugs used can differ across the country. The newest chemical to be used to kill an inmate is etomidate, but what is it, how does it work ...

CBS' Norah O'Donnell: "The AR-15 has been used in six of the deadliest mass shootings in this country"

JOHN DICKERSON (CO-HOST): Welcome, Fran. What are investigators trying to find out from the shooter? FRAN TOWNSEND (CBS NEWS SENIOR NATIONAL SECURITY ANALYST): Well, they want to understand both his mental history -- we know that there was this report from ...