Haroon, who was in his 30s, was arrested by the Crime Investigating Agency (CIA) from the lawns of Minar-i-Pakistan monument in connection with a rape case of an 11-year-old girl at a densely populated area in old Lahore.
A police team was shifting Haroon from one CIA centre to another when he tried to snatch a weapon from a policeman that went off, killing him on the spot, CIA head Umer Virk said.
"Haroon was a serial child rapist and his swabs were taken. After forensic and DNA tests, it was confirmed that he raped the missing minor girl after abducting her," Virk said, adding the suspect would lure minor girls to deserted places and rape them.
The Punjab government has constituted a five-member Joint Investigation Team to probe the country's biggest child abuse scandal involving nearly 300 children which will submit a report within two weeks.
Over 20 accused have been booked in the scandal involving 280 children who were sexually abused and being filmed by a gang which used the videos to blackmail their parents in Ganda Singh village, some 50 kilometres from Lahore.