I think your media sources were likely better and did show the knife in the girl's hand as she is pursuing the other girl in pink. I saw that image -- knife in her hand-- last evening And your sources likely include those phoned in words  “trying to stab us.”   Other sources also carried a photo of the butcher knife on the ground  nearby after the policeman had shot the assailant girl. 

If I recall, the proper police response is -- where there's a deadly threat, police would be using deadly force in stopping that threat.   

Here's a Cornell Law School excerpt --

• . . . . A protective force officer is authorized to use deadly force only when one or more of the following circumstances exists: . . . . 
• (2) Serious offenses against persons. When deadly force reasonably appears to be necessary to prevent the commission of a serious offense against a person(s) in circumstances presenting an imminent danger of death or serious bodily harm 

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