Why Did DC Cop Cover his Body Cam Lens After Shooting Gerald Hall to Death?

At about 1:23 cop covers the lens. From [HERE] No charges will be filed against a D.C. police officer who fatally shot a man while responding to a domestic incident last Christmas morning. 

Gerald Hall, 29, was shot and killed on the threshold of his girlfriend’s house on the 3200 block of Walnut Street in Northeast, shortly before noon Dec. 25.

A statement from the U.S. Attorney’s Office said that Hall and his girlfriend got into an argument, and that Hall turned on all the burners on the gas stove and lit a paper towel on fire. Police responded to a 911 call from a neighbor who said “my neighbor’s getting beat up over there.”

When officers got there, the woman, who they said wasn’t hurt, said no physical fight had happened, and that her sister was coming to take her away. The officers left.

The officers were called back a little later, after the sister told 911 that Hall had locked her out and his girlfriend in. Shortly after the police got there, the statement said, the officers looked through the front door and saw Hall with a knife. The officers told Hall to put the knife down; Hall pushed his girlfriend out the front door. The statement said she had a cut on her arm.

A few seconds later, the door opened, and Hall stood on the threshold, behind his girlfriend. The police cliam he had a knife in his right hand. However, when the cops approached a woman says "the knife is right here, I got the knife." A few seconds later she says "he doesn't have a knife." Within seconds later the cops shot him to death. On video it is not clear what Hall was doing or not doing. 

As his dead body lays collapsed on the floor no knife is visible. At about 1:25 a cop purposefully & briefly covers the lens of his body camera. Thereafter the knife is apparently found. Why did the cop do this? The family should independently investigate the time stamps in the video and do a frame by frame analysis to make sure it has not been edited or remixed Baltimore cop style.  

An officer shot Hall four times; he died at a hospital later.