also fired at Ponty's SUV with his licenced 9-mm pistol.
Then the guards from both sides opened fire, the official said adding the PSOs given to the brothers by Punjab Police were not involved in the firing.
The official said one of those questioned told police that Sachin Tyagi, the PSO of the Commission member, opened fire in retaliation.
However, investigators said Tyagi, who was one of those questioned, tried to save Sukhdev and in the process, he had to open fire. "He opened fire in self defence and save the protectee," the official said.
"We are questioning people. Call records are also being checked," the official said.
The family of Hardeep could not be contacted for comments. This was the second incident of firing at Chadha's residence.
On October 5, gunshots were reported from his house in Uttar Pradesh's Moradabad district.
The three Chadha brothers -- Ponty, Hardeep and Rajinder -- were jointly managing the Rs 6,000-crore Wave Inc, formerly Chadha Group, which has diverse business interests in fields ranging from distilleries, multiplexes, sugar to paper mills.