Table:
text: List of rampage killers
School massacres
School massacres
Perpetrator Date_ Year_ Location_ Country Killed Injured Additional_Notes
Whitman, Charles Joseph , 25 07.31 July 31 / Aug. 1 1966 Austin , TX U.S. 15 32 Shot by police Killed an unborn child
Kretschmer, Tim , 17 03.11 March 11 2009 Winnenden & Wendlingen Germany 15 09.13 9–13 Committed suicide
Lépine, Marc , 25 12.06 Dec. 6 1989 Montreal , QC Canada 14 14 Committed suicide
Harris, Eric David , 18 Klebold, Dylan Bennet , 17 04.20 April 20 1999 Columbine , CO U.S. 13 21 Both committed suicide
Gadirov, Farda , 28 04.30 April 30 2009 Baku Azerbaijan 12 13 Committed suicide
Mz 04.32 2008.9 Mz U.Kz 14.9 14.9 Zz
Menezes de Oliveira, Wellington , 23 04.07 April 7 2011 Rio de Janeiro Brazil 12 12 Committed suicide

Question: On what date did the massacre lead to a list of 21 injured among school massacres by gunmen?