The accident involving the two-wheeler, driven by jail official Probin D Sangma and constable Probat R Marak occurred at Fourth Furlong Tri-junction in Shillong.
The brand new, dark blue private Mercedes with a temporary number was driven by Hek's son Aibansharai Nongsiej, he said.
"The pillion rider (Marak) was declared dead by doctors at Shillong Civil hospital, while Sangma is in critical condition at North East Indira Gandhi Regional Institute of Health and Medical Sciences," Davies Marak, the district police chief of East Khasi Hills, told IANS.
Aibansharai Nongsiej has also been medically examined by the doctors at Civil hospital, the police said.
Police are yet to record the statement of the jail official who is in critical condition.
Minister Alexander Hek said that he is open for a free and fair investigation into the accident.
"It is a very unfortunate incident. Police are conducting the investigation and the law will take its own course," he told IANS.
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