the Lusitania sank after being hit by a torpedo from a German submarine at 1410h. The ship sank with breathtaking speed - it took just 18 minutes - only 8 miles off the coast of Ireland near Kinsdale. Of the 1,959 people onboard (passengers and crew) 1,198 people perished. It was considered the 2nd worst marine disaster after the sinking of the Titanic three years before (April 14, 1912). This Act of War by the Germans was instrumental in bringing the United States into the war.
Here is an article that recounts some new research done suggests the speed of the sinking contributed to a sense of panic that prevented an orderly evacuation from the ship and that - as a result - orderly British passengers and crew perished in greater numbers than younger, American passengers. This was an unfortunate contrast to the experience on the Titanic