This explains it:
https://www.breitbart.com/politics/2024/07/16/reports-police-were-stationed-belo...Reports:
Police Were Stationed Below Trump Shooter,
Who Was Allegedly Spotted Nearly 30 Minutes Before
The report appeared to support a claim from an unverified source posted on X by journalist and Air Force veteran Brian Kimber that said
a local SWAT team was inside the building instead of the roof
because it was hot outside.
The source also suggested a “guy with a weapons case” was reported to local police, but it is not clear whether that is Crooks, and who had reported him.
The source also alleged the Secret Service sniper who killed Crooks
did not take the shot immediately at Crooks because he knew
the local sniper team was supposed to be on that roof, and he had to “deconflict.”
“Complete poo show and failure,” the source wrote in the text.
Another shocking report from local news station WPXI Channel 11 News said law enforcement spotted Crooks on the roof nearly 30 minutes before he fired at Trump.
A source told Channel 11 that a member of the Beaver County’s Emergency Services Unit — which had eight members at the rally, including snipers and spotters — noticed a suspicious man on a roof near the rally at 5:45 p.m. and called it in and took a picture of the person. It is not clear who was informed.