It was the bunch of investors who took the short trade, remember what these guys did was a) rent some shares for X$ promising to return them after some agreed time b) sold them for market rates c) wait a while d) buy them back for (much lower) market rates e) give them back as promised

In essence what they did was negotiate away the share's/bond's owner's rights to sell the shares for a period of time - the person doing the short is betting they'll go down, the person renting out the shares is betting they wont