Anand Pal Singh, posted as In-charge of Hasanpur Kadeem police outpost under Bhavanpur police station, suffered four bullet wounds in the incident last night and was rushed to a hospital, SP (City) Om Prakash Singh said.
Two bullets hit him near the stomach area, while one struck his shoulder, the police official said adding, during the operation doctors removed all three bullets from his body.
Anand's condition is serious but out of danger, he said.
The SI lived in a room of Bajrang hostel at Gadh road.
A fight broke out between two students, who also lived in the same hostel, over the payment of a mobile bill, Om Prakash said.
After receiving the complaint, Anand rushed to the hostel to resolve the dispute.
However, other students joined the fight and one of the groups opened fire on the police official, the SP said.
Four students have been arrested and efforts were being made to nab the others involved in the incident, Om Prakash said.
A 20-year-old girl was stabbed to death allegedly by a jilted lover in east Delhi this evening, police said.