Why might hidalgo have delivered the grito de dolores in a public setting?

Grito de Dolores is otherwise known as the Cry of Dolores. This was an expression which was associated with the revolt of the Mexican against Spain. 

On the morning of September 16, 1810, Father Miguel Hidalgo y Costilla, openly delivered the battle cry for independence, managing to somehow declare war against Spaniards and launching the known Mexican War of Independence. 

He delivered the piece in public to be able to urge Mexicans to take up their arms and join him in the fight up against injustices.