A group of people are outside a brick building.
the rocks were hard
Just because people are outside a  brick building it does not mean there were rocks.
exists p1 x1 x2.(exists x3 x4.(outside(x1,x3) & n_building(x3) & of(x3,x4) & n_brick(x4)) & of(x1,x2) & n_people(x2) & n_group(x1))
exists s1 x1.(n_rock(x1) & Theme(s1,x1) & a_hard(s1))