1. To kill someone that one perceives as a threat or that one feels justified in killing before ensuring that one is absolutely correct. The word "and" is often used instead of a comma. The country's new leader vowed to crack down on anyone associated with dealing drugs, claiming that he was authorizing the police force to shoot first, ask questions later. The sheriff had a policy of shooting first and asking questions later, so while the crime rate was fairly low in his town, so was the death rate.

2. By extension, to take some decisive, negative action before finding out whether it is correct, justified, or necessary. I know you're upset, but you need to consider a few different things before you up and quit your job. Don't just shoot first and ask questions later. When it comes to claims of theft by a member of my staff, my policy has always been shoot first, ask questions later.