Two persons were killed and two critically injured when a seemingly mentally unstable man attacked them “randomly” with the lever of a tube well on Basanti highway, North 24-Parganas, late on Tuesday.

Laxman Routh, 29, and Sajan Mollah, 27, died of head injuries. Haripada Pramanik and Mithun Pramanik are fighting for their lives at the RG Kar Medical College and Hospital in Calcutta.

Nazat police arrested suspected killer Bokul Kalam, 32, and started a murder case against him. The accused was produced in the additional chief judicial magistrate’s court in Basirhat on Wednesday and ordered 10 days of police custody.

Cops, however, appeared clueless about the “random” attack on the four victims, who were associated with a construction farm as masons and were returning home on two motorcycles.

Police and local sources said the attack occurred around 9pm at Boyramari-Kanmari crossing on Basanti highway, where the four parked their bikes for a tea break.

A local resident said: “A little after they parked their motorcycles, Bokul arrived in a violent mood with the lever of the tube well and began to hammer the four at random, targeting the heads. Two of them suffered fatal head injuries and fell on the ground, while the other two tried to resist him but failed and suffered injuries after being hit on their heads too. Bokul was in a murderous mood.”

Local residents called police, who took the four workers to a local hospital where Laxman and Sajan were declared brought dead. Haripada and Mithun were transferred to Calcutta.

A senior police officer from Basirhat police district said: “The reason behind the attack isn’t clear. It appears the suspect is mentally unstable. We have to examine his mental state and if the victims had any prior enmity with him.”

Nazat police sources claimed that accused had a criminal record and had been arrested earlier a number of times for rowdy acts and murder attempts. “He was on bail.... but had never acted so violently prior to this,” a police officer said.