Long Distance Simultaneous Outdoor Wireless System

Hello,

We have two buildings that are 250 ft. away. Each one of them has electric power. In one building there is DVR system with Internet connection and few cameras. We would like to add 4 more cameras to other building and transfer output of those 4 cameras to other building. Those buildings are in point of view. I found systems that would transfer wireless signal from one camera to DVR on long distance, but not 4 at same time. Is there some solution for me? What would be best bet?

Thanks,

Milan