related_tweet: the killings at columbine high school took place 19 years ago and weve had over 70 mass shootings since then. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  since 1968, more americans have been killed by gunfire than have died in all of the wars in american history combined.