The same day another man also attacked students at another elementary school. This knife wielding man left 22 children and one adult injured in the Henan Province of China. There is a difference in the lethality between a knife and a gun. But, in both cases, the assailants were allowed to roam the school hallways far too long. Harris and Klebold caused all the carnage at Columbine High School in just 16 minutes before they killed themselves.