For some reason the old guy decided he was going to play the role of a tough detective, and force her to reveal the identity of "her accomplices". Maybe he's watched too many old cop movies and wanted to solve this crime himself. Sadly, this wasn't a movie, and he murdered an innocent woman.
Ironically, his act of murder will probably ensure the scammer is caught, as the PD will expend far more effort on solving the case now that it's a homicide.
..., and force her to reveal the identity of “her accomplices”. Maybe he’s watched too many old cop movies and wanted to solve this crime himself.
= = =
Maybe he is just fed up with the state of things today, and finally here is a person-person contact to respond to (with way too much force).