I'll give you credit, I read as far as 'Mexican Policeman Attacked By A Flying Humanoid Entity' before writing the guy off as a lunitic.
Okay, maybe he just fainted on the job and made the whole story up to get in the news and get his 15 minutes of fame, be the next Paterson (only, not with Bigfoot) ( "Needless to say that the story broke in the television headlines the next day and a the people of the community awoke to a great controversy. Local tv channels 2 and 34 took the story very seriously and decided to cover all the incidents and follow the case in a huge display of information through all of their newscasts for the next days. " - seems like he got it.
"Several witnesses were interviewed saying that they saw the mysterious black being flying over their homes." - Yeah, Yeah, you always get people jumping on board and saying "I saw it too, let me sell you my story!".
And guess what? It happened - "Norma Alicia Herrera who lives in Colonia La Playa declared in a tv interview that she and her brother saw also the being flying at daytime and that it looked weird."
Or maybe it was a stork or some similar large bird and the human part he just imaged, fear, "stress", shock and late nights can play tricks on your mind ( "maybe it was an excess of work or too much stress that made him believe what he saw, not necessarily what really happened" - my point exactly). Maybe it was some idiot in a suit attempting to start an urban myth.
"She was flying very fast and it took only a second to hit the windshield glass" and "her claws". Okay, if this thing had the weight of a human, and had claws, then such a 'fast' impact, let alone her claws, would have surely left some sort of mark of the glass.
As for 'Note - One look at the young officer's stunned and shocked facial expression speaks volumes. -ed '. Yeah, right

"stood firmly on his account" - if he really was in shock, and surely such an event would be shocking, there would be areas of his memory which would be a blur in the turmiol of events, which could easily distort his perception of events.
"like a horror movie" - Yes, I beleive I saw this scene in Jeepers Creepers.
As for the video 'evidence', looks to me like a gliding bird. An why I ask is the camera deliberately on blur, if its a case of it was far away and they need max zoom to get it, then how did they even see it to begin with.