Hezbollah launched the disturbance because

Fighting in the Lebanese capital Beirut between pro-government groups and supporters of the opposition led by Hezbollah has continued into the night. Reports say at least seven, mainly civilians, were killed and several others wounded. The fight started after the Hezbollah leader Hassan Nasrallah described recent government moves to curb its influence as a declaration of war. Spokesman for the American State Department David Foley, condemned Hezbollah’s actions.
    He said they called on Hezbollah to cease that violent action, and called on Syria and Iran to stop their illegal assistance to Hezbollah, but there was no suggestion of US military reaction in response to the renewed violence.