Check out this footage we got a hold of -- which captures folks in the stands right behind Trump and right underneath the monitor he was referring to in describing a graph detailing the border situation ... with a ton of people right below it looking on.

You can hear DT speaking and making his typical talking points -- and out of nowhere ... you hear what sounds like 3 shots ring out ... with bullets ricocheting off the metal railings.

This is similar to other footage that surfaced Wednesday that showed a similar angle -- but ours is much closer ... and therefore, much more distressing in the fact you can see how panicked people were, not to mention confused about what was going on.

It's unclear if anyone who was filmed in this was actually hit ... but just like we mentioned before, there's a man in a red hat who seems to hit the deck almost immediately after the shots rang out -- which suggests he may have been struck and buckled to the pain.

As we know ... one man -- Corey Comperatore -- was shot and killed as a result of this, and two other bystanders were injured. Trump himself was also injured, getting grazed in the ear.

Thomas Matthew Crooks has been identified as the shooter -- and he was killed just seconds after he got a few rounds off ... getting met with crossfire from Secret Service agents.

While it's a miracle Trump himself wasn't killed ... many have scrutinized the lapse in security at the event -- calling it a total failure on multiple fronts, especially the more we learn about Thomas being spotted on the grounds for at least an hour before he took aim.

There's still no official word on a motive ... but there are countless anecdotes surfacing about Thomas, whom some say was mercilessly bullied in school and an outcast to boot.

The feds are investigating this still ... and a lot of questions remain unanswered.