This is fairly simple
but beginners might miss it in real games
(;AB[qr]AB[pr]AW[qq]AW[pq]AW[or]AB[oq]AB[op]AB[pp]AB[qo]AB[qn]AB[pm]AB[om]AB[nm]AB[mm]AB[mn]AW[nn]AW[on]AW[pn]AB[no]AW[mo]AW[np]AW[nq]AW[mr]AW[ns]AW[ln]AW[lm]AW[ll]TR[np]AW[ml]AW[pl]C[How to respond (localy) to O4?]AP[goproblems]
(;B[po]C[RIGHT])
(;B[oo];W[qp];B[po];W[rr])
(;B[qp]C[no need to give up the kill])
(;B[rq];W[oo]C[no need to give up the kill])
(;B[mp];W[oo];B[lo];W[no]C[what now?...])
(;B[lo];W[oo]C[now what?...]))