Evidence continues to mount that Saturday's attempted assassination of Donald Trump by shooter Thomas Matthew Crooks was allowed to happen, despite ample warning from bystanders, local PD, and even the shooter's parents.

To review:

Three hours before the shooting, security for the rally caught Crooks with a rangefinder and let him go.

40 minutes before the shooting, law enforcement circulated a picture of Crooks crawling around on the ground.

Local PD notified the Secret Service that they had inadequate resources to monitor the building used by Crooks.

The parents of Thomas Matthew Crooks called law enforcement before the assassination attempt to warn them that their son was "missing" and they were "worried" about him.

Local law enforcement observed Crooks leave the area and return three times, during which they took two pictures of him and reported the suspicious activity.

A Secret Service agent in charge of security for the event was on the phone with local and state police about the threat while the shooting took place.

Crowds were shouting at the police to do something about the guy on the roof with a rifle for several minutes.

And now for the kicker: 

After Crooks was positioned on the roof, one cop boosted another cop up to the roofline - only for Crooks to point his weapon at him. At that point, the boosted cop fell.