What would've happened had people not dispersed? Were the tanks and guns just to scare people?

Probably -- we can't assume they would have started firing into the crowd. There weren't any confrontations like this that tturned violent during the fall of the USSR, for instance, and Cuba has also broken up protests without simply shooting people. Most states do everything they can to avoid getting to that point; AES states are not an exception. Crowd control is its own discipline and intimidation is part of it. We also have the fact that they rolled all that stuff out there and backed off.

What should they have done? Do you just open the doors to any unelected group that shows up on the doorstep of the capitol?