Stop calling every murderer a Terrorist
This is an assassination plot - not terrorism. People seem to want to use the word terrorism very loosely.
Terrorism has a specific definition: An action to instill terror in the general public. This requires a general target (could happen to anybody), not a specific target. It is always a Mass Casualty (many murders or injuries) event.
An attack against an influential person in a government is an assassination. It does not have a general target and it is not a mass casualty event.
Even the recent US marine recruiter shootings are not terrorism. First, they are against military targets. An attack against a military target is not a general attack. Second, two people were killed in two separate locations. This fits the definition of Spree Killing, but not terrorism.
For example: A drive-by shooting of a single home or store is not terrorism. Multiple, coordinated drive-by shootings across a neighbourhood are terrorism.
Another example: A jet hijacker is not a terrorist, unless the goal is to use the jet to harm the general public.
Guerrilla warfare is at least as old as the biblical Maccabees. It is much harder to combat random attacks than an attack by an orderly group of people, so people try to classify these attacks as terrorism.