President Obama claimed last night at a Democratic Congressional Campaign Committee fundraiser that Newtown shooter Adam Lanza used a “fully automatic” weapon, even “correcting” himself after calling a semiautomatic weapon.

“Now, over the next couple of months, we’ve got a couple of issues: gun control,” Obama said. “I just came from Denver, where the issue of gun violence is something that has haunted families for way too long, and it is possible for us to create common-sense gun safety measures that respect the traditions of gun ownership in this country and hunters and sportsmen, but also make sure that we don’t have another 20 children in a classroom gunned down by a semiautomatic weapon — by a fully automatic weapon in that case, sadly.”

The gun Lanza actually used was a Bushmaster .223 caliber model XM15 rifle, which is a semiautomatic rifle, according to ABC News. Lanza’s arsenal also included pistols, revolvers, shotguns, swords, knives and other “cutting instruments,” according to search warrants released last week. None of those is a fully automatic weapon.

The difference is a crucial one. An automatic weapon continues to fire until the chamber is empty as long as the trigger is pulled down. A semiautomatic weapon automatically reloads, but one pull of the trigger results in only one shot no matter how long the shooter holds down the trigger.