Black played elsewhere a few moves ago, probably assuming he can live or connect or something, got attacked and resigned after the next white move realizing he can't save his group.
Can you find Zhou Ruiyang's move (and continuation)?
(;AW[dd]AW[ed]AW[be]AW[bf]AW[bg]AW[ai]AW[bk]AW[bl]AW[cl]AW[dk]AW[ej]AW[fj]AW[gj]AW[fi]AW[fh]AW[gh]AW[hg]AW[el]AB[gi]AB[hh]AB[hj]AB[ih]AB[ii]AB[ef]AB[df]AB[cf]AB[cg]AB[ch]AB[ci]AB[cj]AB[dj]AB[ck]AB[ei]AB[eh]AB[eg]AB[bh]AB[bj]AW[dh]AB[if]AB[ie]AB[id]AW[gd]AW[hb]AW[jc]AW[jd]AW[je]AB[jf]AB[gf]AW[hk]AB[ik]C[Kill the black group]AP[goproblems]
(;W[hf];B[he]
(;W[ff];B[fg];W[gg];B[fe];W[ge]C[RIGHT])
(;W[gg];B[ge])
(;W[fg];B[ff];W[ge];B[gg])
(;W[ge];B[gg]))
(;W[ff];B[fg]
(;W[gg];B[fe];W[hf];B[ge];W[he];B[ee])
(;W[fe];B[gg]))
(;W[gg];B[ge])
(;W[ge];B[hf]))