The incident occurred when victim identified as Rinku was on his way to district jail Dasna along with one Shabnam to meet her brother-in-law who is in prison, Station House Officer Raj Kumar Yadav said.
The three accused - Pradeep, Shamshad, and Imtiaz - who were following Rinku shot at him from behind and fled from the spot, Yadav said.
Rinku, who received bullet injury at armpit was rushed to a nearby hospital by police who were informed by Shabnam, he said.
All the accused are still at large, the SHO said, adding that they will be nabbed soon.