What happend to the Lusitania on May seventh 1915?

On May 7th, 1915, at around 2:15, the RMS Lusitania was torpedoed by the German U-boat U-20 on the starboard bow just below the Captain's Bridge and took an immediate list to starboard. Seconds later, a mysterious secondary explosion ripped through the hull from somewhere in the internal bows of the ship, creating a heavy list to starboard. The ship then lost power within minutes and many passengers were trapped below; either in jammed elevator booths or narrow corridors blacked out and impossible to maneuver through. Within 15 minutes or so, Lusitania's decks were completely under water, and within another 3 minutes she was gone. Over 1,100 of the 1,900 passengers that boarded her in New York bound for Liverpool had perished, 128 of them Americans and over 100 children as well; due to the fact only 6 of her 48 boats were successfully launched due to the list. All in all, the sinking of the Lusitania was a pivotal role, along with the Zimmerman Telegram, in bringing America into WW1 on the side of the Allies.