It was mostly planned by a former security guard, seen at left below.

The guard knew when two plastic boxes of cash would be changing hands, and planned the robbery around that.

In a weird twist, one of the arrested men's dads (not the former security guard) was also arrested. When they breached the front door to arrest Nathaniel Greenlee, his father shot a police officer, whose life was saved by a bulletproof vest.

Here is a picture of Nathaniel:

Greenlee was one of the two getaway drivers.