The store has no duty to do a criminal background check unless required by law, which does not seem to be the case here. You have to able to establish a “duty” and “breach of that duty” to make a negligence action. Under the theory being asserted here any store that sold a knife to a felon could be sued if he later hurt someone with it.
Already allowed in Europe...
Its a frivolous lawsuit in its face though - this guy had a desire to murder and if it hadnt been a gun or a knife it was going to be poison or rope or a banner or club or a board with a nail in it!