Another member of the gang was arrested, while the third partner managed to escape, ASP Vineet Bansal told reporters.
The three gang members, who were moving towards Rajnauta village in a vehicle, had an argument with a jeep driver over the issue of overtaking on the highway route, he said.
After a dispute, one of the gang members fired a bullet in the air.
Hearing the sound, the local villagers surrounded them and soon a police team arrived on the spot.
Police arrested one Vikas (21), he said adding, when challenged the second member identified as Surendra Jaat shot himself dead.
Making use of the commotion which broke out, the third member of the gang Billu managed to escape, Bansal said.
Several police uniforms were seized from the vehicle used by the robbers, he added.