The incident took place Monday when the Katwa-Azimgunj Passenger train was entering Bazarsau station in Murshidabad district. A group of assailants attacked Khokon Ghosh, 37, and to the horror of other passengers chopped off his head.
"We have arrested a man who is suspected to be behind the beheading of Ghosh. We are interrogating him and other suspects will be apprehended soon," Superintendent of Railway Police (Howrah) M.K. Das told IANS.
The murder took place Monday afternoon but the body was removed only in the evening when a Government Railway Police (GRP) team finally arrived on the scene.
There were at least five to six attackers and Ghosh, a small trader, was probably murdered over some business-related issue, police said.