Oh!! Philibert Aspairt? I think that's who you mean. He was a hospital worker in 1793 who went into the Paris Catacombs while inebriated. He wandered down to the catacombs for some unknown reason with a lit candle and while I've read conflicting theories about the possibility of his travel to the catacombs but overall we will never know why he decided to delve into such a space especially while intoxicated.
It's speculated that his candle burnt out and he became lost and frantic and ended up dying inside restricted catacomb tunnels. (although I do not know if that restriction is a current restriction or a restriction from back then) Something to note is that, prior to videos and other media you may see now, when in the Paris catacombs, if there is no shafts from the ceiling pouring light in, it's nighttime, or no sepulchral lamps are around. It's pure darkness. Genuine darkness so bad you cannot see in front of you, in back, up down, yourself, where your surroundings are etc. It's quite terrifying so my personal theory is that as soon as his candle burnt out, Aspairt became distraught and probably went into a frenzied state because we, as humans, don't do very well in total darkness, especially in such a foreign place we don't know how to get out of. That and I firmly believe he could've been subject to possibly some mold toxicity/respiratory issues due to the catacombs being very musty/damp like a cellar and mold issues along with the fact he was so frantic could have made everything worse for him. Along with the fact that y'know, dying of starvation/thirst too while lost in pitch black darkness.
Unfortunately, Aspairt wasn't found for another 11 years when quarry workers found him when probably doing repairs to the catacombs and identified him strictly off the hospital keys on his belt. The one thing I have not been able to decipher though is I've read somewhere where they buried him in that same spot in the catacombs out of respect, but I've also heard that his body was hard to move out of the catacombs apparently so they just buried him there and put a plaque nearby. I can't confirm nor deny any one thing in particular because I've never been to said Paris Catacombs nor know the full extent to the story but only that of what I know based off research and some minor videos. From what I gather overall though is that there is a headstone at the place in which he fell with a transcription on it reading to something of the effect of "In the memory of Philibert Aspairt, lost in this excavation of 3 November 1793, found eleven years later and buried at the same place on 30 April 1804."
ALSO unfortunate but I've found out that where his grave is, in a restricted area of the catacombs, is apparently a very popular destination for cataphiles (in which I personally, have no respect for certain groups as they've desecrated and destroyed not only history but the resting dead. But also, there are apparently groups that value discretion, respect and preservation but like to explore the restricted/unexplored areas of the catacombs which I can respect as long as they themselves, are respecting the dead and the space they reside in)
I hope this does your question justice, anon. Though if you are not talking about Mr. Aspairt, are you referencing to the man who was video recording his descent into the Paris Catacombs before he dropped his camera and ran in supposed fear? Because we don't know who that man was nor do we know what happened to him. I've seen theories that it was real and he was just freaked out and ran into darkness and unfortunately most likely passed, or it very well could be fake. That also, we will never know.