RJ85 Range
It is certainly at the top end for an 85 although it is possible to equip them with up to three auxiliary tanks (although don't know if this one had them) Could also have been weight restricted but with a full load of largely male pax would limit scope for that However even if planned with correct minimum diversion fuel it is a tricky airport to fly into from a terrain point of view and if you had a technical challenge at night with minimum reserves it would make life very difficult