Terrifying video captured drug cartel members lining up several people against a wall during a funeral — shooting them dead, cleaning up the scene and leaving behind a bag full of brains.

The gruesome attack occurred Sunday outside a funeral service for the mother of an alleged hitman who had worked for the Jalisco cartel, which has been fighting bloody turf battles in Michoacan against rival gangs.

In the footage, which was captured by a resident of the town San Jose de Gracia, bursts of gunfire break out and smoke covers the scene of the carnage.

On Monday, prosecutors said they could not say how many victims died because the attackers cleaned up the scene, washed the sidewalk and removed the bodies.

Investigators found only a bag full of brains and shell casings at the scene of the massacre.

The Michoacan state’s chief prosecutor said the gang members went to the funeral looking for the hitman, whom officials identified only by his first name, Alejandro.

State Prosecutor Adrián López Solís said the hitman apparently died at the scene.  

The attack occurred only a few blocks from the town hall, where three cops were on duty, he said, adding that police neither went to the scene nor sounded an alarm because “they didn’t have sufficient force” to intervene.

There have been multiple attacks at funerals in Mexico, as cartel gunmen seek to exterminate members of rival gangs during services.

Mayor Jorge Luis Anguiano, whose township includes San Jose de Gracia, said that before Sunday’s attack, a large convoy of vehicles was seen entering from neighboring Jalisco state, but local police didn’t have the firepower to intervene.

“Seeing the number of presumed criminals that were there and given the rules of engagement, we had to retreat,” Anguiano said. “We do not have the firepower to handle this type of situations.”

“In situations like this, municipal governments are left exposed,” he added.

With Post wires