Funny how when the bullets are flying in your backyard it is so much more serious than when it is in the Jews backyard...
The Mohammad and Malvo incident would be equivalent to a couple of Palestinians being responsible for many killings. I'm sure there are some serial killers like that, and that is more akin to terrorism than your typical murders and attempted murders are. But not all Palestinian shootings (or Israeli shootings, to put the shoe on the other foot) are like that.
I think what strikes most people as terroristic incidents are the suicide bombings and mass shootings, including those occasional ones perpetrated by an Israeli, like Baruch Goldstein.