Maswanganyi, who was a Johannesburg Central cluster commander, was found dead on Tuesday in an open field next to the R101 and the M39 in Hammanskraal, north of Pretoria.
"We are shocked by the incident and are working around the clock to bring the perpetrators to book," Petros said.
The police commissioner appealed to the public for any information that would lead to the arrest and conviction of the suspects.
Petros said no threats were made on Maswanganyi's life prior to his murder.
Police officers patrolling the area found Maswanganyi's vehicle parked on the side of the road.
Upon inspection a police uniform and an appointment certificate were found in the vehicle.
The police then went to his home to enquire about his whereabouts, and it was then discovered that he had left for work on the day before his body was found.
After a search that ended at 3am on Tuesday, his body was found with his hands tied behind his back and with no visible gunshot wounds.
Petros said money and personal belongings were found on him and his two cellphones were missing.
"This is a must solve matter, any police killing, irrespective of the rank, is very personal," Petros said.
Police are awaiting a postmortem report to establish the cause of death. However, death by a gunshot was ruled out as the wounds on his chest do not match those made by a firearm
