No, the deadliest mass shooting in American history was at Wounded Knee. The government, which had been confiscating guns, shot 146 people to death.

So that's 146 who died due to an effort to take their guns. Let's not repeat history.

On a similar note, there was the Waco siege. That was also an effort to seize guns. There the US government killed 76, which is also worse than the Las Vegas incident, but partly done by burning people to death instead of shooting them.