Story highlights 12-year-old Tamir Rice was shot and killed last year

He had been playing with a pellet gun in a park near his home

Tamir's family filed a wrongful death lawsuit

(CNN) The much-anticipated police investigation into the shooting death of 12-year-old Tamir Rice has moved into the hands of prosecutors, who will decide what to do next.

The Cuyahoga County Sheriff's Department in Ohio handed over its investigation Wednesday -- more than six months after the boy was shot.

"The sheriff's office received the file on February 13, and has performed an extensive, thorough and unbiased investigation. It is now up to the prosecutor to determine how next to proceed," the department said.

Tamir was holding a pellet gun when a Cleveland police officer shot him November 22. The boy died a day later.

He had been playing in a park near his home.