The San Bernardino County Sheriff’s Office, led by Sgt Michael Warrick, reported the discovery of the bodies, four of which were burned, near Adelanto, about 60 miles (96.5km) northeast of Los Angeles last week.
The incident, linked to illegal marijuana activities, was uncovered after a 911 call was made by one of the victims in Spanish, reporting he had been shot but was unsure of his location.
“As far as the motive, we are confident that this appears to be a dispute over marijuana,” Mr Warrick said on Monday.
Police said the call was traced to the crime scene, where deputies and an air operations unit found multiple gunshot victims and two vehicles, one showing multiple bullet impacts and shattered windows.
The scene at the crime spot was reportedly so grisly that several local TV stations were forced to blur out images captured by their helicopter cameras.
Some of the victims were identified as Baldemar Mondragon-Albarran, Franklin Noel Bonilla (who made the 911 call), and Kevin Dariel Bonilla.
The suspects – Toniel Baez-Duarte, 34; Mateo Baez-Duarte, 24; Jose Nicolas Hernandez Sarabia, 33; Jose Gregorio Hernandez Sarabia, 34; and Jose Manuel Burgos Parra, 26 – were arrested on Sunday.
Mr Warrick said: “There’s certain things at the scene that show a level of violence that obviously raises some interesting questions for us, but at this point in the investigation, we can’t comment on if we believe if this is cartel-related or not.”
Authorities believe the victims met the suspects at the location for a marijuana transaction, which escalated into violence. “It looks like illicit marijuana was the driving force behind these murders, and that’s all we really know at this point.”
The suspects are currently held without bail pending further review by the district attorney’s office.