Thats a dirty cop? 
Looks to me like he did everything correct. 
In fact, I think that the ONLY problem would be his allowing her to reach into her pack, without seeing what was in there. There could have been a pistol. 

And as for the take down, we did not see it. But, offhand, I would say that he was correct to put her on the ground since she was running. 
And compared to the other FCP that beat that girl, this does not appear to be the case. 

FCP, along with Boulder's police, are CONSTANTLY under review by CBI. 
They are considered some of the dirtiest and corrupt police going. 
Then add in Arapahoe, weld, and Larimar county courthouses as being corrupt as well, and you have the vast majority of issues here.