I am trying to reduce this matrix to the reduced one
$$
 \begin{bmatrix}
 -2 & 1 & 1 \\
 1 & -2 & 1 \\
 1 & 1 & -2 \\
 \end{bmatrix}
$$

reduced to 
$$
 \begin{bmatrix}
 2 & -1 & -1 \\
 0 & 1 & -1 \\
 0 & 0 & 0 \\
 \end{bmatrix}
$$

I know how to reduce matrix. but In this case, I have no idea what happens. 

I cannot get $0$'s for third row.