Edibles are usually highly opaque in terms of the strains used and tend to contain at least 5mg THC per dose, sometimes 10, and that's if you trust what's on the label. Due to how edibles are metabolized, the THC remains in your system for longer, too.
You no longer need to "smoke a lot" to consume a great deal of THC, a couple of edibles will do the job. A lot of edible fans don't smoke or vape at all.
We know when using a psychedelic dose, set, and setting become critical.
People taking a strong dose of a psychedelic and expecting it to be no more than a regular pot high might be in for a rude awakening, especially if they treat it casually instead of with great respect, take it in inappropriate circumstances (like at parties or clubs full of people they don't know or trust), etc.
It's no wonder that many people suffer from paranoia and other adverse effects from casual use of edibles. They should really be treating a strong dose of edible cannabis like they do a strong dose of LSD.
I would bet you anything that this person was using a high-potency grade of cannabis and/or smoking a lot of it.
If they just used a little bit of a low-potency strain it's unlikely they would have suffered from paranoia.
"several others became extremely unpleasant and irritable when they weren't high on the drug"
So, wait, these people became nicer to be around while they were smoking and this is supposed to be a bad thing?