Puli Obulesu had opened indiscriminately from the weapon during a failed bid to kidnap K. Nityananda Reddy at KBR Park here on November 19 last year.
The industrialist and his brother Prasad Reddy resisted and foiled the kidnap bid. The accused managed to escape, leaving behind the rifle.
The investigations revealed that 38-year-old Obulesu, a constable in Central Police Lines, Amberpet, had stolen the AK-47 from anti-Maoist force Greyhounds Unit in 2013 and hidden the weapon in the deep forests near Nandyal in Kurnool district (now in Andhra Pradesh).
The accused confessed that he used the same weapon to kidnap a businessman and extorted Rs.10 lakh in February 2014. During the failed kidnap attempt, he fired 20 rounds from the weapon.
Obulesu was booked for attempt to murder and also under Arms Act in both the cases. He was charged within 90 days.
The metropolitan sessions judge convicted and sentenced him to life imprisonment.