A tactic called naked short selling is actually legal but ought to be illegal. A stock is sold to a person. Another person wants it and is allowed to “borrow” it for a time. Many others are allowed to borrow the same share of stock. At any given time if the original owner tries to sell it they will discover they no longer have it. In fact many others claim it via naked short selling. It’s pure legalized theft. The market is a treacherous place because of these types of tactics and there are many tactics.