Other traders and investors are on the opposite side of a transaction, not usually the broker. To say “everyone is selling” is usually an erroneous statement, because in order for transactions to occur there needs to be buyers and sellers transacting to create trades—even though those trades may occur at lower and lower prices. If everyone were to sell, there is no market in that stock (or other assets) anymore until sellers and buyers find a price they are willing to transact at.
When a stock is falling it does not mean there are no buyers. The stock market works on the economic concepts of supply and demand. If there is more demand, buyers will bid more than the current price and, as a result, the price of the stock will rise. If there is more supply, sellers are forced to ask less than the current price, causing the price of the stock to fall.
For every transaction, there must be a buyer and a seller. If the last price keeps dropping, transactions are going through, which means someone sold and someone else bought at that price. The person buying was not likely the broker, though. It could be anyone, like another trader or investor who thinks the price offers an opportunity to make a profit, whether in the short-term or long-term.
*The above answer is borrowed from Investopedia