you hit the nail on the head.....they put a large sell order in...

you hit the nail on the head.....they put a large sell order in at a price they hope is high enough that it doesn't get filled. Meanwhile....other shareholders see this and get a little nervous and start putting sell orders in underneath. This allows the capper to pick off these sell orders and accumulate shares. It happens a lot more then you think.

It is also a good sign that large investors are trying to get ahold of every last share they can because they know it is a strong buy.