The arrested have been identified as Pawan, a resident of Sonepat district of Haryana and second is a minor, a Class 11th student, they said.
The Crime Branch of Delhi Police arrested the duo, who are said to be the members of Sandeep Chitania Gang, when they were coming to Dwarka in South West Delhi to meet one of their associates yesterday.
Police has recovered a .32 bore revolver, six live cartridges, a country-made pistol and a car from their possession.
He said that Pawan came in contact with Sandeep Chitania in 2001 and since then he was an active member of the gang.
"The juvenile joined the gang in 2013. In February this year, Pawan alongwith the juvenile and other associates shot dead another gangster Neeraj in Sonepat due to rivalry," the officer said, adding 16 rounds were pumped into the body of Neeraj.