At a school in Nashville on Monday, a shooter used two AR-style weapons and a handgun to kill three children and three adults. Today on “Post Reports,” we look at the history of the AR-15 and how it became America’s gun.

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Post Reports is the daily podcast from The Washington Post. Unparalleled reporting. Expert insight. Clear analysis. Everything you’ve come to expect from the newsroom of The Post, for your ears. Martine Powers and Elahe Izadi are your hosts, asking the questions you didn’t know you wanted answered. Published weekdays around 5 p.m. Eastern time.