victim: Fish in river
Huge amount of blod has been found in the Nile river. As a result, big number of fish died. God claimed he caused this catastrophe, with his human friends Moses and Aaron. God asked Pharaoh to let Israeli people go and Pharaoh refused, so God poisoned the Nile to show his power.
This did not convinced Pharaoh, as his magicians could do similar tricks as well.