Knife throwing illusion Prop

Imagine a ToT gets to the end of the hall when BANG! A knife apparently slams into it as if thrown over their shoulder. They turn around and see... whatever... or maybe nothing at all.

Magicians use this in their knife throwing routine. They have prop "knives" loaded on a spring type mechanism in back and as they pretend to throw the knife, an assistant triggers the mechanism.

I have a stage show to build where a young actor will need to have a similar device (shaped like a small table or a chair) to shield himself from shuriken apparently thrown by a ninja. I need to build the device, but have no experience and cannot find a tutorial online for free or for sale.

I am hoping some fellow haunters have made something like this or can offer guidance (or a reference) so I can get this built by May. Like any haunt or magic show, it has to work live on stage without making the gimmick obvious.

Anyone?