My Little Chickadee Murder

We went out onto our front porch to eat our lunch and found the nesting Black-capped Chickadee female unconscious on the floor.  
In fact she was dead and one of her eggs that was broken on the porch railing. 
Looking closely at the birdhouse we could see some feathers adhering to the front of it.. 
While examining the dead Chickadee we saw a female House Sparrow land on the birdhouse perch, and the male sparrow make a pass. 
Minutes later the nesting male chickadee came back to the birdhouse and was thrashed by both the male and female sparrows.
Soon, as we watched, the female sparrow came back, entered the nest and threw two more eggs down to the porch floor, smashing them.  
From our research, it seems this is what sparrows do as an aggressively invasive species.
It remains to be seen if they will occupy the birdhouse or if this crime was simply their technique for “owning” the turf because they are nesting nearby. 
The extra photos are for the "Wanted" posters....

Kathy and I are more than a bit heartbroken by this turn of events.