Short answers, pulled from the story.
Three North Vietnamese P-4 torpedo boats from Squadron 135 approached the USS Maddox and fired torpedoes and machine gun fire. The Maddox returned fire with warning shots and a five-inch shell that sank one boat while F-8 Crusader jets destroyed another vessel.
No actual visual sightings confirmed any attack occurred during the evening of the 4th of August 1964. Later analysis showed no wreckage or physical evidence existed at the scene and the North Vietnamese had not sent vessels into the area that night.
President Lyndon B. Johnson interrupted national television shortly before midnight on August 4 to announce an attack by North Vietnamese vessels. He requested authority to undertake military response without mentioning covert operations already underway and decided on retaliatory strikes dubbed Operation Pierce Arrow within thirty minutes.
NSA historian Robert J. Hanyok concluded that agency staff deliberately skewed evidence regarding the August 4 incident to preclude responsible decision makers from having the complete narrative. Ninety percent of signals intelligence that did not support an ambush conclusion was excluded from reports presented to the Johnson administration.
Congress passed the Southeast Asia Resolution granting President Lyndon B. Johnson broad war powers to take all necessary steps including armed force. The resolution gave approval to assist any member state requesting help under the Southeast Asia Collective Defense Treaty.