NEW DELHI: The Central Bureau of Investigation (CBI) Monday arrested key accused Raj Kumar Singh in connection with murder of Bengal chief minister Suvendu Adhikari’s aide Chandranath Rath, reported news agency PTI citing officials.Cops nabbed Raj Kumar Singh in Uttar Pradesh’s Muzaffarnagar.On May 11, a Special Investigation Team (SIT) probing Rath’s murder had arrested three people before widening its probe across multiple states. The cops suspected that hired sharpshooters were brought in from outside West Bengal to carry out the killing with military-style precision.Rath, a close aide of Suvendu Adhikari, was gunned down inside his car near Doharia crossing in Madhyamgram of North 24 Parganas district on the night of May 6, barely 170 metres from his residence.His driver, Buddhadeb Bera, sustained critical injuries in the attack and remains under treatment.According to cops, the attackers executed the operation in barely 50 seconds. A silver-coloured hatchback allegedly intercepted Rath’s vehicle before bike-borne assailants opened fire at close range.The SIT has recovered two motorcycles linked to the crime — one near the airport area and another near rail gates 11 and 12 in Barasat. Preliminary findings suggest the motorcycles as well as the red hatchback had been stolen earlier and fitted with fake number plates to avoid detection.A key breakthrough came after investigators traced a UPI payment made at the Nivedita Setu toll plaza on May 6. Police said the digital trail led them to Jharkhand, where they suspect the silver hatchback used in the murder may have been procured.Sources in the investigation said the attackers deliberately avoided using FASTag and instead made a direct digital payment, which allowed the SIT to track the vehicle’s movement into Kolkata.