Zulfiqar was killed in Islamabad in May while on his way to attend the court proceedings of the Benazir Bhutto murder case.
According to police sources, Umar is also involved in a mosque attack in December 2009 in which 37 people were killed.
Umar was injured when Zulfiqar's Frontier Corps guard Farman fired back at the attackers who were riding a motorcycle accompanied by accomplices in a cab.
According to police, Umar who received three bullets injuries in the firing by Zulfiqar's guard went to District Headquarters Hospital, Rawalpindi, and told doctors that dacoits had fired at him. He was later shifted to a private hospital and also registered a false FIR stating that he was fired upon by dacoits.
Police found the clue from the pistol and Umar's mobile phone which were dropped at the site when he was whisked away by his accomplices in a taxi. His fingerprints were traced and police finally arrested Umar from a private hospital in Rawalpindi three days ago.
Police on Thursday obtained a 14-day remand of Umar from an anti-terrorism court and were currently interrogating him.