Panaji, Mar 26 : The Goa Police on Tuesday claimed to have solved the gruesome killing of a real estate agent Hasan Khan whose battered body was found in his car near a chapel in Bambolim, four kms from the capital, last Friday. Six persons including Robert Gonsalves, a suspended draftsman of the directorate of mines and geology, have been arrested from different parts of Goa, Maharashtra and Karnataka. Police say Gonsalves and his aide Raj Patel had masterminded the murder. Their arrests and subsequent interrogation a day ago resulted in the arrests of four youths - Maruti Bhui, Arun Patil, Ravi Patil and Shivaji Patil - who were outsourced from Belgaum in the neighbouring Karnataka, to kill Khan. Police spokesperson told reporters that Robert and Raj offered a 'supari' to the quartet of Rs 7 lakh for the killing. "Robert is suspended for his alleged role in the illegal mining in the state. During his suspension period, he started real estate business but Khan, who was also in the same business, knew the man was cheating many people. This prompted the murder," he said. Police teams headed by two police inspectors, following the confession of the detailed murder plan by the duo, laid a trap in Kolhapur and Belgaum from where the killers were arrested on Monday.