The teenager's father had announced an AED 5,000 reward to the person who brings back their son.
Dubai Police thanked Shafafet Khan Abdulrashid for his honesty and awarded him a certificate of appreciation.
The UAE Ambassador to Pakistan, Hamad Obaid Al Zaabi, made the announcement at a meeting in Karachi on Thursday.
A Chicago police panel announced the decision over the 2014 killing of 17-year-old Laquan McDonald.
Japanese police have identified the detained suspect as Shinji Aoba but he has not yet been arrested.
15 people have been killed after a minibus filled with illegal migrants crashed in Turkey.