Officials said Namdhari, former Uttarakhand Minority Commission chairman, was arrested by a team of Delhi Police and taken to New Delhi for questioning on the double murder.
After his arrest, Namdhari said he had already told police what he had seen on the fateful day. "I had known Ponty Chaddha since 1994 and I was with him when the incident took place. I took him to hospital and also lodged an FIR," he said.
He added that he had left his cellphone numbers with Delhi Police and had come to Uttarakhand after police allowed him to leave. "They (Delhi Police) told me to go and said they would call me when I was required," he added.
He said he had switched off his phone for two days as he was being hounded by the media for statements.
Namdhari was sacked as the chairman of the Uttarakhand Minority Commission after the shootout. He has more than three dozen cases against him, which include murder, attempt to murder, dacoity and several others.
His personal security officer Sachin Tyagi is alleged to have shot Hardeep after he opened fire at Ponty.
In his statement to Delhi Police, Namdhari said that he went to the farmhouse with Ponty.
He told police that Hardeep began shooting at them the moment they arrived. Namdhari said he slipped out of the rear door of the vehicle and hid behind it.
