The victim, sub-inspector Balwan Sharma, who was posted as in-charge at Kharawar police post, was shot at by an unidentified youth near Kheri Saadh village on the National Highway No. 10, late on Friday night.
Constable Harvinder Singh also sustained gun-shot wounds in the attack and was admitted to the Post-Graduate Institute of Medical Sciences (PGIMS) here. Doctors said he was out of danger.
The police officials were returning in their jeep after investigating a case when the attack occurred.
Police said that the jeep was stopped by three workers of the industrial township on the outskirts of Rohtak. They told the police officer that a youth with a weapon had snatched their money and mobile phones, and could be nabbed from that area, where he was roaming.
The police officer managed to get hold of the young man and made him sit in the jeep. The young man opened fire at close range from a pistol, killing the sub-inspector.
He fired at the constable too, and escaped.
The workers who had complained also fled from the spot.
A man passing by on a motorcycle saw both the police officers lying on the road in a pool of blood, and informed the local police. The victims were rushed to the hospital, where doctors declared the sub-inspector dead.
No arrests have so far been made in the case. A case of murder has been registered against an unidentified young man.
This is the fourth attack on police personnel in Rohtak, the home district of Haryana Chief Minister Bhupinder Singh Hooda, in the last six months.
A retired inspector and a sub-inspector were murdered, and four other policemen sustained injuries in different incidents.