They only have to decapitate the government. They’ll have to fight the national police as well, but there’s no reason to kill unarmed civilians for the coup to be a success. There are many ways to disperse crowds.
They are shooting into crowds from copters. They also may have no choice -- Erdogan has still very strong popular support ( more in Ankara than in Istanbul ) and the crowds contain large number of "Allahu Akhbar" people... the people who like being martyred.
Videos of a copter firing can be found at Southfront
https://southfront.org/live-updates-the-turkish-revolution/#disqus_thread