Calderon said last year that 6,500 Mexicans died in drug violence in 2008 . Calderon visited Mexico last week to discuss killings of 15 people . Latest killings will be his third since taking office in 2006 . Calderon 's resignation has been criticized by some . He is leading a campaign to rid Mexico of drug trafficking .
Calderon visited Mexico last week to discuss killings of 15 people . Latest killings will be his third since taking office in 2006 . Calderon 's resignation has been criticized by some . He is leading a campaign to rid Mexico of drug trafficking .