Travis Kelce was only playing follow-the-leader when he walked into a restaurant to keep on celebrating after the Kansas City shooting -- 'cause we've now learned Patrick Mahomes planned the whole thing, and was there as well.

Multiple sources with direct knowledge tell us the get-together at the Granfalloon Restaurant And Bar in K.C. Wednesday evening was actually spearheaded by the Chiefs QB -- and, according to our sources, he had the idea shortly after the Super Bowl win.

We're told Pat was the one who rented the place out. Cops were on hand for crowd control. Travis obliged when several cops asked him for selfies.

While we only got pics of Travis rolling into the establishment hours after the shooting ... our sources tell us Patrick was also in attendance, as were other Chiefs players.

Unclear who else was there at the Granfalloon -- but we spoke to the restaurant owner ... and he said a few other players had rolled in, and that it was a private event. Unclear exactly what the guys were doing inside -- presumably, eating, drinking, etc.

The question, of course ... why would Pat, Travis and other teammates go out in public and keep their good time rolling after a massive tragedy?

It's something many have been wondering since we broke the story of Travis attending this gathering ... with a beer in hand.

As we reported ... the shooting left one person dead, and 22 others injured with gunshot wounds. Cops have said this didn't appear to be a terror attack -- but rather a dispute between parties.

Now that we're learning Patrick was in the mix for this party -- it makes ya wonder what sort of thought process went into their decision to go through with the party ... especially since they were all well aware of the shooting.