When confronting Nathaniel, do not kill him and find out that it was Hubert. After finding out Nathaniel is not the killer, instead of using Axii to stop him from hurting Sweet Nettie, choose to fight and kill him. Combining the reward for killing Nathaniel then Hubert will net you the most loot for this quest.

Is there any way to save Patricia Vegelbud?

Speak to the coroner and you can ask some questions that reveal suspicious answers about Hubert. Then you can look over the body and Hubert will find a note saying the next victim- Patricia Vegelbud. Head over to the Vegelbud Residence as fast as you can to save her.

Can you catch the Vegelbud killer?

Travel to the Vegelbud Estate, argue your way in past the gate guard, and speak with Ingrid, Priscilla's daughter. She'll eventually lead you to her mother's bedroom, where you almost catch the killer red-handed. Chase off after him, avoiding the estate guards, but alas - they prevent you catching the murderer.