Ex-UFC star and former American sniper Tim Kennedy says many people need to answer for the disaster that was the Trump shooting … and he thinks folks need to lose their jobs.

Tim — who was once a U.S. Army Special Forces sniper — tells TMZ he believes the training of those immediately around Trump during the Pennsylvania rally Saturday was most definitely not up to par for protecting him against the shooter, Thomas Matthew Crooks.

Donald Trump has Secret Service snipers to thank for taking out the gunman who apparently tried to assassinate him — because just a second after he fired … they took him out from an opposite roof, all of which can now be seen in new video.

He says the site survey team was supposed to identify any locations that could pose a threat to Trump, which he believes they utterly failed to do … and now, he thinks key people at the Secret Service and beyond should have to pay for it with their careers.

Take a listen … Tim says that in addition to DHS Secretary Alejandro Mayorkas resigning — he’s the guy technically in charge of the Secret Service BTW — he thinks the current director of the Secret Service, Kimberly Cheatle, should also bow out and exit her position.

Plus … he says some of the agents who were with Trump that day should get the boot too.

In terms of how exactly this debacle could be allowed to unfold, TK got into that with us here too — and he’s got a pretty interesting theory on what he believes went so very wrong.

Basically, he chalks it all up to a huge communication problem … telling us the Incident Command System (ICS) should’ve had one key person in charge for direct communication with the Secret Service for a seamless chain of command on how to respond.

As we’ve reported … there’s been a lot of scrutiny directed at the federal agency after Crooks was able to get up onto a roof outside the PA rally and fire off shots at DT.

The Secret Service has since said they’ll be going above and beyond to protect Trump at the Republican National Convention following the attempted assassination … and they’re looking into exactly how Crooks was able to get shots off with so many seeing him.