toward the sterate. small boats carrying u.s. naval reaction forces raced out boarding without firing a shot but u.s. sailors discovered the four american hostages shot. when our team got on board the yacht, there were hostages who were still alive and we applied and gave first aid immediately to them. but they were fatally injured. reporter: mysteriously, two pirates were already dead. moments later, u.s. forces killed two more pirates below shooting one and knifing another. 15 pirates in custody. there were explicit warnings to mariners about the regions, the dangers and the pirate activity in this area. reporter: this was the deadliest pirate attack on americans in modern history and it really illustrates how far pirates are now roaming offshore. up to 1,500 miles. to put that in somewhat of a perspective that is the area of