The Bihar Police have arrested the son of a legislator from Lalu Prasad's Rashtriya Janata Dal for allegedly stabbing a young man in an incident of road rage in Aurangabad. Kunal Pratap, son of RJD legislator Birendra Sinha, allegedly beat up and stabbed 26-year-old Pintu Kumar for overtaking his car in the Obra area of Aurangabad district on Friday.