The state police on Friday arrested one of the two activists of the hardline Hurriyat Conference who were allegedly involved in a conspiracy to engineer violence in Kashmir valley by planning the killing of 10 to 15 people during a procession. The police swooped down at a place on Narbal-Magam Road and arrested Shabir Ahmed Wani, district president of the Hurriyat Conference led by Syed Ali Shah Geelani.