Spoiler for Duck-tective: Reborn as a Flock episode 47 Read at your own risk
It was Jane, the hatted woman. It's simple. She was the one who hid the knife, which was a circus knife all along. Circus knives are plastic knives with an arch in it to make it resemble a cut [body part]. The reason she did it was to practice for her drama lessons. She used it on her unconscious father, since he was abusing her for getting bad grades in Drama class. She used sleep mushrooms to knock her dad unconscious, as evidenced as there was leftover mushroom in the trash can. It was claimed by Harold the glasses man that he saw a woman with the same shade of hair walk out of the joke store. The dead man with the gun was just a random suicidal attempt. Sorry for everyone who accidentally read these spoilers.