Two sniper teams opened fire, one federal one local. Assassin was killed by federal agent. Four sniper teams were in position — two federal, two local.

BETHEL PARK, Pa. – Thomas Matthew Crooks, the 20-year-old would-be assassin who opened fire on former President Donald Trump’s Pennsylvania campaign rally Saturday, hid the weapon in advance, according to a Secret Service source.

It was not immediately clear where he hid it, however. By the time agents spotted him on the roof, he was already holding it.

“We went from golf range finder to AR-15, and now we have to fill in the gap,” the source told Fox News.

When authorities first observed Crooks carrying a golf range finder Saturday, he was perceived as a “person of interest” but not a “threat,” authorities said Thursday.

Range finders were not banned from rally events at the time, but authorities are expected to review the list of items that are not allowed.

He did not become an official threat until he was seen with a weapon.

There were four counter-sniper teams stationed around the rally, according to the Secret Service – two from the agency and two provided by local law enforcement.