Another case of a white police officer fatally shooting a young African American came more sharply into national view Wednesday with the release in Cleveland of surveillance footage showing that the officer opened fire within seconds of arriving at the scene.

The incident, which occurred Saturday as the nation awaited a grand jury's decision on whether to indict the officer who killed an unarmed black teenager in Ferguson, Missouri in August, set the city of Cleveland on edge after days of modest street protests over the shooting.

The video shows the final actions of Tamir Rice, 12, as he paced around a Cleveland park playing and posing with what police said appeared to be a handgun.

Responding to a 911 call, a police cruiser pulls up rapidly to a small gazebo where Tamir has been sitting. Almost immediately, Officer Timothy Loehmann, a 26-year-old rookie, opens fire on the boy after stepping out of the passenger side of the car.

Tamir, whose gun turned out to be an Airsoft BB pistol, falls.

The video was released Wednesday at the request of the boy's family, who said in a statement: "It is our belief that this situation could have been avoided and that Tamir should still be here with us."

"The video shows one thing distinctly: the police officers reacted quickly," the statement continued. It also called for the community to remain calm.

Last year, the Justice Department opened an investigation into the Cleveland Police Department over allegations of excessive and unreasonable deadly force.

Cleveland Deputy Police Chief Edward Tomba said at a news conference Wednesday that "the release of this video is in no means an effort to try and explain the actions of the Division of Police or of the young man."

"We are honoring the wishes of the family in releasing this and also in the spirit of being open and fair with our community," Tomba said.

Tamir's shooting happened two days before the announcement of a St. Louis County grand jury's decision not to indict Officer Darren Wilson in the fatal shooting of 18-year-old Michael Brown, which set off violent demonstrations, looting and vandalism in Ferguson.

There were no immediate signs of street demonstrations in Cleveland following the video's release.

The grainy footage, which lacks audio, shows Tamir pacing up and down a sidewalk, swinging the gun in his hands, pointing it a few times and chatting on a cellphone.

A man shown sitting under a nearby gazebo made a 911 call, telling the dispatcher, "There's a guy in here with a pistol, pointing it at everybody," according to audio of the call.

The caller said the gun is "probably fake, but you know what, he's scaring the s--- out of people." He later said, "I don't know if it's real or not." He described Tamir as "probably a juvenile." He eventually left the park.

But the information about the gun possibly being a "fake" was not mentioned to the officers in a call to them about a young black male with a gun in a park.

Loehmann, who is white, according to public records, has been a police officer since March. Officer Frank Garmback, 46, drove the patrol car. He is a certified field training officer who joined the force in February 2008.

Both officers have given statements and have been placed on administrative leave, per department policy.

As the police cruiser pulled up quickly in front of the gazebo where Tamir had been sitting, Loehmann shouted from the car three times for Tamir to show his hands as the boy approached the car, Tomba said. Loehmann got out of the car and, within two seconds, shot Tamir from about 10 feet away.

Authorities said the Airsoft gun resembled a semiautomatic handgun and lacked the orange safety marker intended to signal that it is not a real weapon.

"Shots fired, male down, um, black male, maybe 20," one of the officers radioed. "Black handgun."

Within four minutes, two other law enforcement officials arrived, and one performed first aid on Tamir, Tomba said. An ambulance came minutes later. Tamir died Sunday of gunshot wounds to his torso.

Results from the police investigation will be sent to the Cuyahoga County prosecutor's office. The evidence will be presented to a grand jury for possible charges, as is the policy with all fatal police shootings.

Cleveland Mayor Frank Jackson said Wednesday that Tamir's death wasn't connected to what is happening in Ferguson.

"Whether there was Ferguson there or not, that doesn't matter to me. What mattered to me was it happened in Cleveland, and it happened to a child," Jackson said. "It's about the child, the loss of his life, the grieving of his family, and what we have to do as a community."

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Washington Post researcher Alice Crites contributed to this report.