Police: Motive unknown in Wisconsin office shooting

Authorities say they still don't know why a Wisconsin software company employee went to his office with a pistol and extra ammunition and opened fire on his colleagues, seriously injuring several before he was fatally shot by police.

Why female shooters are rare

As the investigation continues into why a female shooter opened fire at YouTube headquarters, data show that it's rare for women to carry out such shootings -- making Tuesday's incident unusual.