Saints Row 2 - Island population increase

Near the top of the map in the water, there are three small Islands not far from the mainland. If you go to the island that is the furthest West (Judging by the map) you should see some people fishing. Take one of the these people hostage and throw or kill them. When you turn around there should be several more people who have appeared out of nowhere running around on the island.

Note that this glitch can cause so many people to appear on the island at once, that it sometimes causes the Xbox360 to lag considerably.