Beaver County SWAT team members assigned to protect the former president during his rally in Butler, Pennsylvania earlier this month sat down for an interview with ABC News airing Monday morning.

In a small clip shared on Good Morning America Sunday, eight members of the SWAT team say they had no contact with the Secret Service prior to the shooting ... and, no way to contact the former president's detail either.

Check out the vid ... one of the officers says he thought it very odd they didn't have a sit-down with the Secret Service before the shooting -- and only spoke with anyone connected to the detail after the first shots were fired.

The members of the team will reportedly talk in more detail about feeling partially responsible for the shooting ... knowing communication goes both ways.

This lack of communication claim between local cops and Secret Service is just the latest bombshell blunder by the organization ... which has already seen its chief resign amid revelations they saw the shooter 20 minutes before he fired on the 45th prez.

Kim Cheatle -- the former Secret Service chief -- called it one of the biggest operational failures in SS history.

The ABC interview tomorrow morning will certainly tell some of the story ... but, TMZ's got you covered with a deep dive into the biggest story of the year.