Depends on our definition of “assault weapon.” If you mean “an object that can kill someone”, then yes, all school shootings involved assault weapons.
I’d even go so far as to say all murders are committed by things that can kill someone.
“Assault weapon” is a typical leftist word twisting and spinning, with always the same aim, manipulate others with emotion.
They will say everything and anything if it help them to reach their aim, damned with facts, reason and truth.
The latest trendy codeword in their novlangue arsenal was “weapon of war” (as if knife was not used in wars!).