<Tr> <Th> 11 </Th> <Td> Edmond post office shooting </Td> <Td> 1986 </Td> <Td> 15! 15 (inc . the perp .) </Td> <Td> 6 </Td> <Td> Semi-automatic pistols </Td> <Td> </Td> </Tr> <Tr> <Td> Columbine High School massacre </Td> <Td> 1999 </Td> <Td> 15! 15 (inc . both perps .) </Td> <Td> 24 </Td> <Td> Multiple types of firearms </Td> <Td> </Td> </Tr> <Tr> <Th> 13 </Th> <Td> Binghamton shootings </Td> <Td> 2009 </Td> <Td> 14! 14 (inc . the perp .) </Td> <Td> </Td> <Td> Semi-automatic pistols </Td> <Td> </Td> </Tr> <Tr> <Td> Fort Hood shooting </Td> <Td> 2009 </Td> <Td> 14 </Td> <Td> 33! 33 (inc . the perp .) </Td> <Td> Semi-automatic pistols </Td> <Td> </Td> </Tr>

When did mass shootings start in the us