The definition of terrorism is "the unlawful use of violence and intimidation, especially against civilians, in the pursuit of political aims." And I think some of the situations we have witnessed in recent history supports the definition, causing political discussion about certain topics such as gun control. It has the same outcome (not on such a large scale, of course) as acts such as 9/11, people were killed. Even though the stereotypical thought of a terrorist is usually someone from a different country, people in our own country have the same ideas. In my opinion, I see no difference.
A terrorist, by definition is someone who harms or threatens civilians with a political aim, someone who is trying to make a statement to the nation. Lately, the mass shootings in the news, mostly school shootings, have been by people who were angry and hurting others in their anger. I am by no means justifying anyone actions, or saying that it makes sense why anyone would inflict harm to those people, but it is not and should not be called terrorism.
We overly complicate so many things. If it is proven that an act of killing someone for any reason is found to be premeditated then call it just that: Murder. The more people you kill the heavier the scales upon your judgement. Period. I'd include state sanctioned murders as well.
Many people think terrorism is any form of massacres or destruction. That is false. Religious violence isn't terrorism either. If someone does a massacre/explosion/etc. And they are motivated by religion, then they aren't a terrorist at all. They're a militant religious extremist. The established definition of terrorism is someone who does violence, murder, or destruction, especially against civilians, for a political aim. This has been the established definition of terrorism for a long time. Before the word terrorism lost its meaning, that was how terrorism is defined. The columbine killers aren't terrorists. Real terrorists are Timothy McVeigh and Osama bin Laden, who are both politically motivated.