The college campuses in West Bengal appear to have turned into killing fields.
On Tuesday, an anti-social shot a police officer dead in Garden Reach in broad daylight. The violence that culminated in the shooting had begun as part of students' election at a local college.
Sub-inspector Tapas Choudhury, 56, was on duty outside the Harimohan Ghose College campus. Doctors said he bled to death before he could be brought to the hospital.
Another man, 26-year-old electrician Tahir Hussain, sustained injuries in his left hand after being hit by the butt of a revolver.
"The violence was a result of clashes between the Congress student wing Chhatra Parishad and Trinamool Chhatra Parishad," said V Solomon Nishikumar, deputy commissioner, port division.
The students' union elections were to be held on February 28.
In the evening, police arrested four men, including one Sheikh Suhan, who was seen firing the shot in television footages. He was arrested from the Garden Reach area.
The other three held included his uncle Ibne Saud, Ghulam Talib and Abdul Matin.
Locals said Suhan is a supporter of the ruling party. Shortly before the shooting, he was seen standing next to local Trinamool councillor Md Iqbal.
"I went there to quell the tension. Many people gathered at the spot and if the assailant happened to be there, I cannot be held responsible," Iqbal said.