CHANDIGARH: With the Punjab Police, in coordination with Central Agencies and Delhi Police, having arrested the second perpetrator of Chandigarh Grenade Blast case within 72 hours, the probe has revealed that USA-based wanted gangster Harpreet Singh alias Happy Passia, who is working on the behest of Pak-based Babbar Khalsa International (BKI) terrorist Harvinder Singh alias Rinda and ISI, handled the accused by providing explosives, weapons, and logistical support but reneged on promised rewards to the accused persons.