The CID has arrested Mehsud last week from Manghopir along with three accomplices.
A suicide jacket, two rockets and other weapons were also recovered from their possession.
SSP CID Fayyaz Khan said a police team had arrived in Karachi from Khyber Pakhtankhwa to interview Mehsud.
Mehsud had told the police that he along with his accomplices Kalimullah and Naqeebullah had attacked Rashid Hussain, Mian Iftikhar Hussain’s son.
Rashid Hussain was killed in the attack while his cousin Amjad had been injured.
Mehsud further claimed he had targeted Rashid on the orders of Baitullah Mehsud and Hakimullah Mehsud.