This.
I used to fly around 75 (sometimes 7.5 feet) AGL (AWL for you nerds) through there. You get close to the Reagan traffic all of the time. Easy to get complacent. However, the tower could have said something to keep them from smashing into each other. Maybe ask PAT about his altitude deviation or told them to turn immediately. The tower could have looked outside with his eyeballs and seen this accident coming.
Once again, real bummer for the lost. If PAT was heading home they were only a few minutes away, the CRJ was on final. Everyone was almost home safe.