The Facts

• However, Butler County Sheriff Michael T. Slupe told CNN that officers had discovered the shooter on the roof after receiving calls of suspicious activity. He added that one officer hoisted another up to peer over the ledge but let go to take cover after the shooter turned the rifle on him.After Donald Trump survived an assassination attempt at a Pennsylvania rally on Saturday, Pres. Joe Biden has "directed an independent review of the national security" to probe how a shooter could manage to evade the US Secret Service and get onto a roof in close proximity to a presidential nominee.

• Biden also said he has asked the Secret Service to review all security measures ahead of the Republican National Convention, which begins in Milwaukee on Monday, adding that the investigation is underway to find a motive for the assassination attempt.

• The FBI has identified Thomas Matthew Crooks, 20, as the alleged gunman. An investigation into Crooks' background and possible motive is ongoing.