The trigger-happy official identified as Inspector Olakunle Olonade had shot the traffic official, Adeyemo Rotimi after he stopped his vehicle for violating traffic rules.
The operative had reportedly told Adeyemo during an argument that ensued that he had no right to stop him.
While that went on, the suspect was said to have immediately reached for his gun in the vehicle and shot the deceased.
He was, however, immediately mobbed by onlookers before he could make an escape.
He was severely beaten before he was handed to the police.
Lagos police spokesman Chike Oti said in a statement that the killer officer died on his way to the station.
“Although he was later rescued by teams of policemen drafted to the scene, he later gave up the ghost while being rushed to a hospital for treatment,” Oti said.
Lagos police boss Imohimi Edgal has, however, ordered a posthumous trial and dismissal of Olonade from the Force.