According to reports, the incident took place late on Tuesday night. Reuters video filmed in the early hours of Wednesday (September 2) showed forensics and police officers at the crime scene.
As of Wednesday, the death toll stands at eight with 14 others sustaining injuries at the funeral.
Authorities have not yet reported on the arrests of the gunmen but investigations are ongoing.
Mexico has been blighted by gang violence for many years, with successive governments failing to tackle the problem. According to the latest data available, more than 34,600 murders were registered last year, a record.
Overall murders in Mexico are up 1.6% in the first seven months of the year compared to the same period in 2019.