Give the DA a bit of time. They want to make they have a solid case.
... can't tell if sarcasm...
In the event that it's not, just what evidence do they expect to find? Unless they are pursuing a conspiracy charge and plan on charging other people, I cannot imagine there being anything else for them to investigate.
Did violent neighbor tackle
Senator Paul? Does Senator Paul have serious and potentially life threatening injuries as a result of that attack? That's all they need for felony charges. (And, for the Feds, it's: "Did violent neighbor attack Rand Paul? Is Mr. Paul a sitting Senator?")
I suppose there is one other possibility. If they are wanting to charge terrorism, they could be looking more deeply. However, my faith in the law enforcement community to do their jobs and punish violent leftists is waning significantly. (Which REALLY ought to frighten the leftists, but they don't seem to care the kind of resentment that unequal application of the laws engenders.)