Let \( z \in \mathbb{C} \) be such that \( \frac{z^2 + 3i}{z - 2 + i} = 2 + 3i \). Then the sum of all possible values of \( z^2 \) is:
\( -19 - 2i \)
\( 19 - 2i \)
\( -19 + 2i \)
\( 19 + 2i \)