 Command the high ground. If there is high ground and line of sight, you have to block it with some kind of structure. He says he sees that as a key failure at the Butler, Pennsylvania rally where 20-year-old Thomas Crooks had an elevated position with a line of sight to the former president at a range of less than 150 yards. The head of Homeland Security called the assassination attempt a Secret Service failure and the director of the Secret Service will face an inquiry on Capitol Hill next Monday.