RD Sheokand, chairman of the Haryana Environment Impact Assessment Authority, was killed in a road accident on the national highway-1, near Nirmal Kutia, in the district on Monday evening.
Three others who sustained serious injuries in the accident were Sheokand's friend RS Lamba, Vikas Chauhan (official gunman of independent Panipat MLA Om Prakash Jain) and driver Rakesh Singh.
They were referred to the Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh.
Civil surgeon Dr Shiva Kumar said Sheokand, an ex-IAS officer, was declared dead at the hospital.
Police said Lamba was driving the car and he, along with Sheokand, was heading towards Delhi.
Superintendent of police Shashank Anand said Panipat MLA Jain was in chief minister Bhupinder Singh Hooda's convoy that was heading towards Newal airstrip, near Karnal.
Hooda had gone to Panipat to meet one of his ailing relatives and Jain had joined him.
Jain's gunman Chauhan was travelling in Jain's private car (HR-30-K-000, which was being driven by Rakesh Singh.
The superintendent of police said after Rakesh lost control over the vehicle, Jain's car rammed into another car (CH-09 (T)-6146), carrying Sheokand and Lamba, after crashing the divider on the elevated highway near Sector 7.
Panipat MLA OP Jain, Zile Ram Sharma and Dharam Singh Chhokar, Congress MLAs from Assandh (Karnal) and Samalkha (Panipat) respectively, rushed to the trauma centre where the injured were taken.
The trio was seen coordinating with the district and hospital administration for medical tests and treatment.