This is sort of an addition to an interesting thread Allan started earlier this month:
https://community.ricksteves.com/travel-forum/italy/oplontis-anyone-heard-of-it
A forum search didn't turn up any previous posts with mentions of, or links to, this bit of history so here ya go:
There is only one recorded, firsthand account of the AD 79 eruption, and it was written by a 17 or 18 year-old nephew and namesake of his uncle, Pliny the Elder. Uncle Pliny (formal name Gaius Plinius Secundus) was at that time serving as admiral of the Roman fleet at the port of Misenum (today's Capo Miseno) and he perished during an attempted rescue mission during catastrophic event. It is in the form of two letters from the younger Pliny to the historian Tacitus, and you can read translations of them in the link attached. Scroll down to letters LXV and LXVI if the link doesn't take you directly there.
https://www.gutenberg.org/files/2811/2811-h/2811-h.htm#link2H_4_0065
Apologies in advance that they aren't in paragraph form, so may be a little laborious to wade through, but they provide an interesting eyewitness report! (Edited a typo)