It's a wild narrative. It goes a lot deeper than just these murders, but also includes his time in prison and a reversal of fortune after these murders. Dumas basically copied most of his plot verbatim and then fleshed it out.
I did go into the podcast episode on the chances of it being a falsified narrative, but having studied this era a lot I'm convinced that at the very least the Paris Police archives had the dossier of the entire case, and that Peuchet (the archivist) was trying to piece it together when he died. The archives burned down in 1871, so we'll never have any account besides his.