This is either war or war crimes depending on what exactly happened.
There seems to be a trend of calling every terrifying event “terrorism.” People sometimes colloquially refer to even non-political mass shootings as terrorism.
I believe it’s important to separate different types of mass violence. For example a gang-related mass shooting might be de-escalated by a mediator engaging the belligerents, whereas a war crime should be sent to international criminal court and a terrorist should be dealt with in a manner to minimize the earned media attention.
Do we have a word for "imperialist government uses violence against people to achieve political goals"?
Because "it's not terrorism because it's a state" is always gonna stink of trying to dodge the topic on a technicality.