TECOMÁN, Mexico — He slumped in a shabby white chair, his neck unnaturally twisted to the right. A cellphone rested inches away, as if he had just put it down. His unlaced shoes lay beneath outstretched legs, a morbid still life of what this town has become.

Israel Cisneros, 20, died instantly in his father’s one-room house. By the time the police arrived at the crime scene, their second homicide of the night, the blood seeping from the gunshot wound to his left eye had begun to harden and crack, leaving a skin of garish red scales over his face and throat.

This was once one of the safest parts of Mexico, a place where people fleeing the nation’s infamous drug battles would come for sanctuary. Now, officials here in Tecomán, a quiet farming town in the coastal state of Colima, barely shrug when two murders occur within hours of each other. It’s just not that uncommon any more.

Last year, the town became the deadliest municipality in all of Mexico, with a homicide rate similar to a war zone’s, according to an independent analysis of government data. This year it is on track to double that figure, making it perhaps the most glaring example of a nationwide crisis.

Mexico is reaching its deadliest point in decades. Even with more than 100,000 deaths, 30,000 people missing and billions of dollars tossed into the furnace of Mexico’s decade-long fight against organized crime, the flames have not died down. By some measures, they are only getting worse.

The last couple of months have set particularly ominous records: More homicide scenes have emerged across Mexico than at any point since the nation began keeping track 20 years ago.

Some of the crime scenes, like the room where Mr. Cisneros was found dead in his chair, had only one victim. Others had many. But their increasing frequency points to an alarming rise in violence between warring cartels. Criminal groups are even sweeping into parts of Mexico that used to be secure, creating a flood of killings that, by some tallies, is surpassing the carnage experienced during the peak of the drug war in 2011.