People gather at a vintage ice cream truck to receive traditional ice cream.
The people are enjoying a stroll through the park.
People enjoying  a stroll are not generally referred to as gather.
exists e1 p1 s1 x1 x2 x3 x4.(at(e1,x2) & Topic(x2,p1) & exists e2 s2 x5 x6.(Theme(e2,x5) & Actor(e2,x2) & v_receive(e2) & n_cream(x5) & of(x5,x6) & n_ice(x6) & a_traditional(s2) & Theme(s2,x5)) & n_truck(x2) & of(x2,x4) & n_cream(x4) & of(x2,x3) & n_ice(x3) & a_vintage(s1) & Theme(s1,x2) & Actor(e1,x1) & v_gather(e1) & n_people(x1))
exists e1 x1 x2 x3.(n_park(x3) & n_people(x1) & through(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_enjoy(e1) & n_stroll(x2))