B Nandarwal (34) was attending to customers during rush hour when a group of people poured highly inflammable liquid and set him on fire at around noon in Motphran area of the city.
Nandarwal was admitted to a hospital in a critical condition.
East Khasi Hills SP M Kharkrang and Additional District Magistrate D M Wahlang rushed to the spot to ascertain the situation.
Police have not ruled out the possibility of the involvement of pro-Inner Line Permit activists in the attack.