They fell at the hands of David and his men.

1 Chronicles 20:1-8
In the spring, at the time when kings go off to war, Joab led out the armed forces. He laid waste the land of the Ammonites and went to Rabbah and besieged it, but David remained in Jerusalem.  David took the crown from the head of their king—its weight was found to be a talent of gold, and it was set with precious stones—and it was placed on David’s head. He took a great quantity of plunder from the city.
In the course of time, war broke out with the Philistines, at Gezer, at Gath.
These were descendants of Rapha in Gath, and they fell at the hands of David and his men.
The Bathsheba and Uriah episode fits between 20:1 and 20:2. The Chronicler regularly leaves out details of private life, in line with his purpose of focussing on true kingship and the true worship, so this may not be a 'whitewash' or cover-up- especially since the story was already known from the earlier records.
Why?
The Chronicler regularly leaves out details of private life, in line with his purpose of focussing on true kingship and the true worship.
Emphasize the kingship and worship is the main purpose of the Chronicler. 
David was doing everything smoothly when he became king of Isreal. All of the nations around them were subdued to Isreal.
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歷代誌主要對象是祭司，歸回的以色列人。神憐憫人，祭司赦免人。這時候以色列人已經經歷神的處罰，現在不再是責備的時候。是憐憫，重新站立的時候。此時必須要倚靠主，撒旦及個人的私慾會使人跌倒。災難叫人煩惱最後反而使人得著益處
讓戰敗者服勞役，使用鋸子，耙子等。
神能改變人的生命，改變性格，脫胎換骨。
神向大衛應允的都一一成就了！
完全降伏於神，神必使我們成為新造的人
How?
Before the Lord, there is no my own mind and my way. There is the way the Lord arranged for me and it is better than I hoped.