 Hearing those facts, you might conclude that somehow this 20-year-old had managed to elude detection by Trump's protective detail until he was able to open fire. But that's not true. The Secret Service and local authorities were aware of the gunman long before he climbed on the roof. Quoting from CNN, the shooter was spotted by local law enforcement who thought he might have been acting suspiciously near the event magnetometers on Saturday, according to a senior law enforcement official. They put it out over the radio to keep an eye on him. And that information was passed on to the Secret Service as well.