An FIR has been lodged at Jagdishpur police station against Gopalji, Rudra Pratap Singh, Neelkamal, Uday Pratap Singh and five unidentified persons, said Superintendent of Police Heera Lal.
Gopalji is the cousin of Uttar Pradesh minister and controversial MLA Raghuraj Pratap Singh alias Raja Bhaiyya.
The case has been lodged under Section 302 (murder) and 307 (attempt to murder), among others, of IPC, the SP said.
Mahendra's close aide Suresh Kumar was also killed in the shootout while the driver of his car was injured.
Jang Bahadur Singh, is a former president of Uttar Pradesh Rajya Bhandaran Nigam, which is a state minister-rank profile.