The officer standing next to the body does not appear to be in any distress.
Has it been determined if it the officer is, in fact, Officer Wilson?
I seriously doubt it.
Officer Wilson would have been quite occupied by then.
See blackdog’s reply at http://www.freerepublic.com/focus/f-news/3194542/posts?page=102#102
The injury isn’t necessarily immediately known. However the existence of the injury shows that an attack occurred - and the officer did know THAT.