A man died after allegedly shooting himself in the head in the back of a police van taking him to the Calcutta police station on Tuesday night.
Mpumalanga police spokesman Superintendent Abie Khoabane said the police arrested the man and locked him up in the van before driving to the police station at about 9.30pm.
"According to information at my disposal the officers heard the loud bang of a gun in the back of their vehicle before reaching the station and immediately stopped.
"They took cover and checked what was actually happening, only to find the suspect lying in a pool of blood with a bullet wound to the head and a gun next to his body," Khoabane said yesterday.
He said the policemen who had made the arrest were under investigation for failing to search the suspect when they made the arrest.
"We fail to understand how the suspect got into the police vehicle with a gun without our members noticing that," Khoabane said.
"The explanation might be that they simply did not bother to search him.
"The incident leaves us with no alternative but to conduct investigations against them."
Khoabane said the identity of the victim would be released once his next of kin had been notified.
He said the man was arrested in connection with a murder that committed in June.