Assuming 3 hours fuel, I'd have thought the weights would be within limits. Dunno about luggage.
Well, depends on the individual weights - a quick look in a generic graph shows either just about in or just about out. Add high alt / high temp and you're setting yourself up for trouble. In other words, even if notionally within limits, a PA-28 loaded to the gunwales will have no reserves left of any kind at high altitude.
Temps on the accident day were about 8 degs C above standard (you can check on weather.com) assuming they left around or shortly after the point of lowest temp. I don't know the baro on the day, but assuming standard, going over these mountains would have brought the plane very close to the edge of the envelope.
Tragically, sounds like another heavy/hot/high accident.