Violent protests follow Philadelphia police shooting

(NBC News) Violence erupted in Philadelphia Monday evening following the fatal police shooting of a man armed with a knife.

Dozens of arrests were made and 30 officers injured in the unrest that followed the shooting.

A witness captured that confrontation on cell phone video.

NBC News cannot verify what occurred before or after the events shown in the video.

Police say when they arrived they found the man, later identified as 27-year-old Walter Wallace, acting erratically and waving a knife.

In the video you can hear an officer yelling for Wallace to put the knife down as he moves toward, them before the officers open fire, killing him.

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