Los Angeles: A disgruntled Indian doctoral student who had been working on his thesis for 10 years is believed to have killed his professor at the University of California-Los Angeles after the latter refused to give him a passing grade.

Mainak Sarkar, 38, who was born in India before coming to the US to study, shot engineering professor William Klug, 39, dead in his office before turning the gun on himself, the Daily Mail quoted the Los Angeles Police Department.