We arrive in Culiacán early Wednesday morning, and it doesn't take long to see signs of the fear that has settled in on the city. Masked federal police patrol the roads in caravans of armored trucks, and by nightfall, the streets are empty.

Over 100 drug-related homicides have been reported this month alone in Culiacán, a city of just under 800,000 people. The daily toll is somewhere between four and five bodies a day. While much of the violence has occurred between narco comandos, as the local newspapers call them, and the police, the brazenness of the attacks, which often occur during the day and in busy parts of the city, have shocked residents.

Many have been caught in the crossfire. Only Ciudad Juarez and Tijuana, the border towns that serve as the frontline for the battle between the fractured Sinaloa-based cartel and its rivals in the Gulf of Mexico and on the border, have been bloodier.

On our first day in Culiacán, four people are shot dead, including a 56-year-old doctor executed in his own office.