Why did citizens of Paris surround and take over the bastille on July 14th 1789

The lower classes of France knew that for a revolution to work, they needed weapons. The best place to get these was at The Bastille, a French prison that was well-equipped and poorly guarded. On July 14th, it was stormed and the governor of the prison was mutilated. All of the prisoners (about 10) were freed and the weapons were stolen.