Dilip Rabha (52), who was training 20-year-old elephant Shankar for the past two years, was pulled down from the animal's back and trampled to death while it was being taken for a bath.
After killing the Mahout, Shankar sat near the body and prevented anyone to come near him. A team from Nandankanan Zoo reached the spot and tranquilized the elephant.
"Shankar sometimes becomes violent. However, it was calm today. We are yet to find out what exactly prompted Shankar to kill the Mahout," Divisional Forest Officer Siba Narayan Mahapatra said.
Earlier, Shankar had left another Mahout injured.