The accused, identified as Deepak, was arrested from the spot and the gun used in the crime along with 11 live cartridges was recovered, they said.
The incident took place around 7.30 pm on Thursday near MS Block, Timarpur, where staff patrolling heard a gunshot and rushed to the spot.
"The staff found a man lying in a pool of blood on the pavement while locals were trying to snatch the gun from the accused," said the source The victim, identified as 60-year-old Surendra Singh, a retired sub-inspector from the CISF, was rushed to HRH Hospital where doctors declared him brought dead.
The bullet had struck his left cheek, causing multiple pellet injuries to his face, he said.
Initial inquiry revealed that the family was preparing to shift to their native village in Uttarakhand after Surendra Singh's retirement from CISF six months ago.
They hired a tempo and their belongings were being loaded when an argument broke out between Surendra and Deepak over who would sit in the front seat, said the source.
As Surendra insisted on occupying the front seat due to the loaded items, Deepak turned aggressive, fetched his father's licensed gun, and allegedly shot him, police source said.
A case of murder has been registered and further investigation is underway, he added.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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