Some bumblebees are more aggressive than others.
 
If what your friend wants to knowis, will they attack him, then
he could find out by slowly approahcing the nest and seeing if
the bees notice him or not.  That would give him an idea as to
how nervous he ought to be regarding their proximity to his house.
 
Foraging bees almost never sting - it's being near the nest he
should worry about.
 
Good luck
Liz Day
presently in New York City, USA
receiving mail at [log in to unmask]
(that's Lday, not ONEday)