The video shows Tamir Rice walking around in the park holding what police say was an air pistol. A 9-1-1 caller reported him to officers, saying Rice was a juvenile and the gun was probably fake.
According to audio tape released by police, the dispatcher didn’t pass that information on to officers.
In the low-quality video, a car is seen pulling up on the grass very close to Rice. Authorities say an officer told him three times to show his hands as the car was approaching.
Police said around one-and-a-half to two seconds elapsed before the officer fired and Rice doubled over.
When officers called for assistance after the shooting, they mistakenly identified Rice as "maybe 20" years old, according to dispatch audio.
Almost four minutes elapsed before a detective and FBI agent arrived to provide first aid, and EMS arrived three minutes after that, police said.
Deputy chief Ed Tomba said the case will be turned over to the county prosecutor.
“This is not an effort to exonerate," Tomba said. "It’s not an effort to show the public that anybody did anything wrong. This is an obvious tragic event where a young member of our community lost their life.”
The officer who shot Rice was identified as Timothy Loehmann, a 26-year-old rookie who started with the force this year. The driver is Frank Garmback, who has served with Cleveland police since 2008. Both gave statements to investigators, Tomba said, and are on leave.
"It is our belief that this situation could have been avoided and that Tamir should still be here with us," Rice's family said in a statement. "The video shows one thing distinctly: the police officers reacted quickly."
Tomba said after an investigation, police will turn the case over to Cuyahoga County Prosecutor Timothy McGinty -- who has said he'll present the case to a grand jury.