Rinku had suffered deep stabbing injuries and was shifted to ICU, the police said.
A Delhi Police head constable was stabbed when he was trying to stop a fight between an auto-rickshaw driver and some men in southwest Delhi's Chhawla area, police said on Monday.
The incident took place Sunday evening when Assistant Sub-Inspector Sunil and head constable Rinku of Chhawla Police Station were on patrolling duty in the Qutub Vihar area, and got a call at 8.35 pm about a fight in the area, a senior police officer said.
When the patrolling staff rushed to the spot, they found some men were having a row with an auto driver, Deputy Commissioner of Police (Dwarka) Harsha Vardhan said.
As police intervened, one of the people fighting the auto driver stabbed Rinku twice and ran away. The man was identified as Sunny alias Shooter, a known criminal of the area.
Rinku was taken to a hospital, where he was found to have deep stabbing injuries, the DCP said. He is currently in ICU, he added.
After the incident, police launched a manhunt for Sunny and his other accomplices and got a tip off that he was at a house on Bhai-Bhai Road in Qutub Vihar.
When police raided the house around 2.30 am, they were fired at by Sunny. Police also fired three rounds, hitting him in his legs.
Sunny was arrested and taken to a hospital where he is under treatment, Mr Vardhan said.
In all, police arrested three people from the house and seized a country-made pistol, three live cartridges, and a knife from them. A hunt is on to to arrest other people involved in the incident, police said.