Gunmen had stormed into Trinamool's office in Kharagpur and opened fire.
Seven people have been arrested by the West Bengal Police in connection with the murder of a Trinamool leader's husband and his friend in a shootout at Kharagpur on Wednesday.
While the police have revealed the identities of four people who have been arrested, the identities of three accused will be revealed only after an identification parade is completed by the police.
Trinamool councillor Pooja Naidu's husband Srinivas Naidu, and his friend Dharma Rao, were declared dead when they were taken to a hospital in Kolkata - a three-hour journey by road following the shoot-out at the Trinamool Congress office in Kharagpur.
The police say the conspiracy to kill Naidu was hatched due to enmity with several groups. "Several meetings were held and plans were made following which a number of criminals assembled and committed the murder on January 11," West Midnapore Superintendent of Police Bharati Ghosh said.
The motive behind the crime was the hatred for Naidu and to create an adverse law and order situation in Kharagpur, the police say.
"Some people wanted to disrupt law and order in Kharagpur and create a crisis here. They wanted to take control of several areas and there are several important persons who have given logistical support and planned this entire operations," Bharati Ghosh added.
Some of the plans were hatched outside the state, the police have revealed. Srinivas Naidu, locally known as Srinu, was at the office of his wife Pooja, the councillor from ward 18, when a group of unidentified men rushed in around 2.30 pm on Wednesday. The men, who had driven to the office located on Kharagpur's outskirts, hurled bombs, stormed in, opened fire and, within minutes, fled. The councillor was unhurt.
The police say that they cannot confirm at this stage if there is any political influence behind the crime. Only further investigation can reveal this, the Superintendent of Police added.