A mayor in Mexico's western state of Michoacan has been shot dead while campaigning for President Felipe Calderon's sister in her run for the governorship.

The state Attorney General's Office says Mayor Ricardo Guzman of La Piedad was passing out campaign material Wednesday night when a man pointed a gun at his head and fired.

Gubernatorial candidate Luisa Maria Calderon told the Televisa network the shots came from an SUV. Calderon belongs to the National Action Party like her brother. She is a contender in the Nov. 13 state elections.

Michoacan is Felipe Calderon's home state and where he launched his armed offensive against drug cartels. Several mayors have been murdered across Mexico in drug attacks and others in political disputes.