This is a 3 volley salute, commonly known here in the Philippines as a 21 gun salute. It is usually performed during a funeral of heads of state, members of the military or of any citizen of great societal significance. This one specifically was performed on the funeral of the father of a friend of mine.
The history of the 3 volley salute came from an old battlefield custom in which both warring sides would cease all hostilities in order to clear the battlefield of the dead and injured. The 3 volley salute was then performed in order to inform both sides that they can now resume hostilities.
Today the 3 volley salute is performed as an honorable gesture in recognition of the services, sacrifices and contributions of the deceased to society.