The 70-year-old ex-serviceman, Ram Kishan Grewal, had consumed poison in the lawns behind Jawahar Bhavan, which houses the Ministry of External Affairs, on November 1. He was rushed to RML Hospital where he died during treatment.
Grewal, along with three of his companions, had come to the city apparently to submit a memorandum to the Defence Ministry over the issue of OROP.
"One of the persons accompanying him, Rajkumar is a social activist. Prithvi and Jagdish are ex-servicemen. They were called for questioning at Crime Branch office," said a senior crime branch officer.
All of them were let go after questioning.
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They all hail from a village in Haryana's Bhiwani district and were in regular touch with Grewal for the past several months, police said.
Meanwhile, teams are verifying the authenticity of the suicide note left by Grewal and are examining the toxicology report.
The Crime Branch team led by DCP(Crime) Bhisham Singh is conducting inquest proceedings in the matter.