2 0 1 7 , ▁D ens ley ▁launched ▁The ▁Vi ol ence ▁Project ▁with ▁psych ologist ▁J ill ian ▁Pet erson ▁of ▁Ham line ▁University . ▁D ens ley ▁and ▁Pet erson ▁built ▁a ▁database ▁of ▁all ▁public ▁mass ▁shoot ers ▁since ▁ 1 9 6 6 ▁c oded ▁according ▁to ▁ 1 0 0 ▁different ▁variables . ▁Their ▁research ▁on ▁mass ▁shoot ers ▁included ▁in - depth ▁analysis ▁of ▁K - 1 2 ▁school ▁shoot ings ▁and ▁how ▁the ▁Columb ine ▁High ▁School ▁mass acre ▁became ▁a ▁blue print ▁for ▁future ▁mass ac res . ▁D ens ley ▁and ▁Pet erson ▁are ▁critical ▁of ▁active ▁shoot er ▁lock down ▁dr ills ▁in ▁schools ▁for ▁tra um at izing ▁young ▁children ▁and ▁normal izing ▁school ▁violence . ▁ ▁In ▁a ▁ 2 0 1 9 ▁op - ed ▁for ▁the ▁Los ▁Angeles ▁Times , ▁The ▁Vi ol ence ▁Project ▁presented ▁a ▁new , ▁hope ful , ▁framework ▁to ▁understand ▁mass ▁shoot ings . ▁Based ▁on ▁a ▁study ▁fund ed ▁by ▁the ▁National ▁Institute ▁of ▁Justice , ▁Pet erson ▁and ▁D ens ley ▁found ▁mass ▁shoot ers ▁had ▁four ▁things ▁in ▁common : ▁( 1 ) ▁early ▁child hood ▁tra uma ▁and ▁expos ure ▁to ▁violence ▁at ▁a ▁young ▁age ; ▁( 2 ) ▁an ▁ident ifiable ▁gr iev ance ▁or ▁suic idal ▁crisis ▁point ; ▁( 3 ) ▁validation ▁for ▁their ▁belief ▁system , ▁have ▁studied ▁past ▁shoot ings ▁to ▁find ▁insp iration ; ▁and ▁( 4 ) ▁the ▁means ▁to ▁carry