The WC established that Mooney was the first law enforcement officer to go to the sixth floor of the Texas School Book Depository (TSBD) after the shooting, and that Mooney was the officer who discovered the sixth-floor “sniper’s nest.” Mooney headed up the stairs from the second floor to the sixth floor at no later than 12:50. No federal or local law enforcement officers were on any of the upper floors of the building between 12:35 and 1:10.
No federal or local law enforcement officers were on any of the upper floors of the building between 12:35 and 1:10.This is clearly not the case.
Marrion Baker, along with Roy Truly, reached the seventh floor at approximately 12:35 PM. As the were coming back down to the first floor in the elevator, they stopped on the fourth floor where Baker had a quick chat with Inspector Sawyer. Sawyer had entered the TSBD around 12;35Pm and made his way up to the fourth floor with another officer and a mystery employee from the TSBD. He had his interaction with Baker on the fourth floor at approximately 12:40PM.
However, both these men were in full uniform and cannot be mistaken with the plain clothed deputy sheriffs Mooney saw on his way up to the sixth floor.
Mooney entered the TSBD no sooner than 12:40PM.
He took the elevator, which stalled on the second floor. He had a quick look around the second floor then made his way up to the sixth floor via the back stairs. It was at this time he crossed the two men coming down the stairs. This took place at approximately 12:45PM.
Mooney went up to the sixth, had a good look around on his own, went up to the seventh floor and helped out there before returning to the sixth floor and walking straight over to the southeast corner, where he discovered the "cubby hole". After alerting other officers on the sixth floor of his discovery, he shouted down to Fritz, who was entering the building at 12:58PM
So who were the two plain clothed deputy sheriffs Mooney encountered around 12:45PM?

This is the report of Deputy Sheriff Jack Faulkner, written up on the day of the assassination.
In it he reports that immediately after the shots he made his way to Elm Street where he was trying to find out what was going on.
He reports that "a small negro boy came up to a Dallas Uniform officer" and told him the shots came from the TSBD. The is is clearly Amos Euins talking to Harkness. This happened BEFORE Harkness radioed in this information at 12:36PM.
Faulkner immediately went to the TSBD where he was met by McCurley, Wiseman and Loraine and they "went to the top of the building and started checking the floors going down from the top in search of the assassin".
They make it to the third floor where they interview some people after which they make their way back up to the building. It is some time after this that Mooney makes his discovery.
It seems that Faulkner, a plain clothed Deputy Sheriff making his way down from the seventh floor, is at least one of the men Mooney encountered. I'm guessing Bill Wiseman was the other.