BBC have a break down of the security failings at the Trump rally. There’s a lot to unpack but there’s a series of major security failings documented.
Btw I’ve seen lots of people post that the shooting wasn’t real, was a crisis actor, was staged, conspiracy theories from 4chan etc.
That kinda thing has no basis in reality. Somebody died. Multiple people were injured. The local police left the shooter on the roof for two minutes while running around trying to work out what to do - they didn’t have a communication plan. Nobody had secured the roof before the event.
What happened is simple: a series of security failings, and a shooter.
There’s a good write up here on the law enforcement body cam videos of the Trump assassination attempt.
Long story short = security failure. Local police thought Secret Service were supposed to have secured the roof, Secret Service thought police had it, comms terrible, people didn’t know what to do etc.