Police on horseback at an outside protest.
Police are making an arrest.
Just because the police are outside protest, does not mean the police are making an arrest.
exists s1 x1 x2 x3.(a_topic(x1) & at(x1,x3) & n_protest(x3) & a_outside(s1) & Theme(s1,x3) & on(x1,x2) & n_horseback(x2) & n_police(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_make(e1) & n_arrest(x2) & n_police(x1))