Travis Scott was mostly oblivious to what was going on around him Friday night during his Astroworld set -- including the fact people were dying around him ... TMZ has learned.

Sources with direct knowledge tell TMZ ... Travis is utterly devastated over what transpired Friday, and he's beside himself over it. We're told he's been crying since it all happened, and he's an emotional wreck.

We're told he wasn't aware of the extent of what was happening around him -- people going into cardiac arrest, etc. -- and thought what few people he did see being attended to were folks who'd simply passed out from dehydration.

It's not uncommon for that type of thing to happen ... especially at a packed festival like this.

We're told Trav did, in fact, stop the show a few times to check on people who appeared to be unconscious or in distress, alerting security and other personnel over to them for assistance. But, our sources say he simply didn't realize how bad it actually was.

Not just that, but we're told neither he nor his camp were even informed about deaths or hospitalizations until after the show was done. As we reported ... a total of 8 people have died thus far, and dozens more were injured and hospitalized, including several minors.

As for Kylie ... our sources say she too is quite upset, and is trying to console Travis as best she can by being there for him.

Like we first told you, there were sightings of at least one person getting jabbed in the neck with a needle ... something Houston PD confirmed as accurate. It's unclear if that may have led to all of the cardiac arrests, or just one or a few -- but it'll certainly be looked at as part of the wider probe.