Los Angeles, Jun 2 (IANS): 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.

Sarkar appears to have had a long-running feud with Klug.

In a blog post uploaded on March 10 under his name, Sarkar wrote that the professor "stole all my code and gave it another student". Sarkar branded him a "sick man".

The post, which was uploaded to a blog called Long Dark Tunnel but has since been deleted, says: "William Klug, UCLA professor is not the kind of person when you think of a professor. He is a very sick person. I urge every new student coming to UCLA to stay away from this guy."

"My name is Mainak Sarkar. I was this guy's PhD student. We had personal differences. He cleverly stole all my code and gave it to another student. He made me really sick."

"Your enemy is your enemy. But your friend can do a lot more harm. Be careful about whom you trust. Stay away from this sick guy," the blog reads.

However, a source told the LA Times that Sarkar's claims were "psychotic", adding that his characterisation of Klug as a thief was "absolutely untrue".

On the UCLA website, Sarkar was listed as part of the Klug Research Group, a team of six post-doctoral and PhD students researching biomechanics.

The website shows Sarkar has been studying for his PhD since 2006 with no graduating date, two years longer than any of the other researchers.

Around 200 armed police, SWAT officers, FBI agents and firefighters were called to the campus to reports of at least three shots fired inside the Engineering IV building around 10 a.m. on Wednesday, before finding the bodies of both men alongside a 9mm semi-automatic pistol.

Officers say a piece of evidence, believed to be a suicide note, was found at the scene -- but they refused to give any more details.