Mexican authorities have not said whether they see the slayings as targeted. They come after a year of heightened political violence.

Two top aides of Mexico City Mayor Clara Brugada were shot dead after being ambushed by gunmen on a motorbike in a daytime attack in the city center on Tuesday. The victims were the mayor's private secretary,

The professional assassins carefully planned the attack, using a clean weapon and three stolen vehicles with fake license plates to cover their tracks