The notorious 'thak thak' gang stole a bag with an iPad and Rs 20,000 in cash from the car of former Delhi Police Commissioner B.K. Gupta in north Delhi, the police said on Monday. Police said the incident occurred on Saturday when Gupta and his friends were shifting their luggage from one car to another at Majnu Ka Tila in the Civil Lines area. "While B.K. Gupta and his friends were shifting the luggage from one car to another, which was unlocked and parked behind it, an unknown man stole a bag with an iPad and Rs 20,000 cash and escaped," Deputy Commissioner of Police Jatin Narwal told IANS. A resident of Greater Kailash in south Delhi, Gupta along with some friends was going to play golf in Chandigarh from Delhi. "A case of robbery has been registered against the unknown man. The place where the robbery took place has no CCTV camera," Narwal said. "Primafacie it appears that the notorious 'thak thak' gang is involved in this robbery. The investigation is underway and we have interrogated some suspects. We will soon nab the accused," the officer added.