Scholar MM Kalburgi was shot dead at his home in Karnataka on Sunday

The police in Karnataka will investigate whether the killing of scholar MM Kalburgi on Sunday is linked to the murders of two other rationalists, Narendra Dabholkar and Govind Pansare.Four police teams have been formed to investigate the murder of Dr Kalburgi, a well-known rationalist and Left ideologue who had faced threats from rightwing Hindu groups. Two of these teams will travel to Kolhapur and Pune, the hometowns of Narendra Dabholkar and Govind Pansare in Maharashtra, senior police officer Pandurang Rane told NDTV on Tuesday.United by the murders, all three families have agreed to meet in an attempt to speed up justice.Dr Kalburgi was shot dead on his doorstep in Dharwad town by two men who came on a bike and asked for "sir". The police believe hired killers were used."The killing has been done professionally. Professional killers are very unusual to this region," Mr Rane said.In August 2013, Mr Dabholkar, an anti-superstition activist, was shot dead in Pune while he was out on a morning walk in Pune. In February this year, social activist and veteran CPI leader Govind Pansare -- who was leading a campaign against toll tax among other issues -- was shot dead in similar circumstances in Kolhapur.In all three cases, there were two men who struck in the morning and used a bike to get away.Mr Rane said in the case of Dr Kalburgi, all possible motives were being investigated, "including the property angle." He added that groups that had protested against him are also being investigated.The family of the 77-year-old rationalist has alleged that he was killed for his beliefs.The professor had received many threats to his life and had been given armed escort, which was withdrawn recently on his request.A Bajrang Dal activist who had posted a threatening tweet after Dr Kalburgi's murder was arrested yesterday but released hours later.The Vishwa Hindu Parishad has asserted that no rightwing group had threatened Dr Kalburgi.