The accused Kailash and Hari Singh were arrested on a tip off by police near Chatth Puja Park on Dabri Road in Palam, said Surender Kumar, DCP (south west).
The accused were also involved in a number of robberies, snatching and vehicle lifting cases, besides supplying locally manufactured firearms to criminals in the area, he said.
They used to threaten morning walkers with firearms and rob them of their valuables.
Arrested Hari Singh is a history-sheeter and had come out of jail in 2010 after serving a sentence in a murder case, said the officer.