PATNA, July 24 -- Around 9 am on July 18, a day after Bihar gangster Chandan Mishra was shot dead at Paras Hospital in Patna, the West Bengal police received an alert from their counterparts in Bihar that the gang was heading towards West Bengal. The gang members were not using any mobile phones to stay off the grid. So, there was no way the police could track them using their mobile tower location, officials said. "The accused persons in the car had switched off their mobile phones. Hence, we were not able to track them with the help of their mobile phones. We had the vehicle's number and its description. The only way to track them was the vehicle in which they were travelling," said a senior IPS officer involved in the case. Sleuths of the West Bengal police and Kolkata Police took the help of some advanced gadgets and software to pick up digital footprints of the vehicle as it moved from one corner of the city to another. The killers had no inkling. "Based on inputs that were received, we were certain that the vehicle would reach Kolkata by the evening of July 18. We started analysing FASTag and toll plaza data on the route that the vehicle would possibly take to reach Kolkata such as Maithon, Dankuni, Palsit and Vidyasagar Setu," said the officer. The white-colour vehicle entered Kolkata around 10:30 pm on July 17 through Vidyasagar Setu, which connects Kolkata and Howrah over the River Hooghly.HTC...