We’re literally already in one. We’ve been in a cold civil war for about a decade now (arguably the past few decades), and the war’s been growing hotter with every mass shooting and tragedy like this one.
This is how civil wars are fought in the modern age. It’s not all fancy suits and muskets. It’s large swaths of people with opposing views killing each other over it at every opportunity, like this one.
Why do you think school shootings happen? Or mass shootings in general? The vast majority of them are committed by members of right-wing hate groups and it’s part of this civil war they’ve been waging against the left. The whole point is to eradicate the left or force them to submit to their will.