Andy Lopez Cruz was in fact carrying a pellet gun shaped like an AK-47 assault rifle when killed in Santa Rosa, northern California on Tuesday.
His distraught father Rodrigo Lopez said: “It is not right what they did to my son.”
Lieutenant Paul Henry, who is investigating the incident for the Santa Rosa Police Department, said two Sonoma County Sheriff’s deputies had been patrolling near the boy’s home on Tuesday when they saw him walking with what appeared to be an assault weapon in his left hand.
One of the deputies, who did not immediately realise that the person he was seeing from behind was a child, shouted twice: “Put down the gun,” according to Lt Henry and a police statement.
“The subject turned toward the deputies, and as he was doing that the barrel of the weapon was rising toward the deputies,” he said. The deputy then fired several rounds, killing the boy.
The incident took place against a backdrop of growing concern about police shootings in California, where a spate of such incidents in the city of Anaheim, south-east of Los Angeles, prompted protests in 2012. Concern over seven fatal police shootings in three years in Sonoma County fuelled calls in 2000 for a civilian review board, but none was established.
Displaying a real AK-47 assault rifle next to the plastic one recovered from the scene, Lt Henry pointed out the similarities in their appearances. The pellet gun was shorter, but lacked a bright orange component meant to mark it as a toy rather than a real weapon.
Pellet guns, which use compressed air or other gases to fire pellets or spherical balls, are sometimes made to resemble actual assault weapons. Police also found a plastic handgun tucked into the dead boy’s trousers.
“It’s a tragic event,” Lt Henry said. “It’s tragic for the family, the community and the deputies.”
According to friends and family, Andy Lopez had a good sense of humour and liked to tease his friend Luis Diaz’s older sister, Ana. But he also appeared to have had some difficulties.
According to his father, he was expelled from Lawrence Cook Middle School in Santa Rosa, which is north-west of San Francisco in California’s wine country. On Tuesday, he had been sent home early from his new alternative school, for what his parents described as lingering too long at a local store during a break.
Later in the afternoon, his father said, Andy took the pellet gun, which had been left by another child, and made plans to see his best friend, Luis. When Andy did not return home later in the day, the family called the Diaz home and learned he had not arrived there.
Mr Lopez said he then stepped outside, saw the police cars and commotion and eventually realised that the motionless object lying on the ground was in fact his son.
The officers involved in the shooting have been placed on leave and the incident is being investigated.
On Monday, a 12-year-old boy at a Nevada middle school shot his teacher dead before turning the gun on himself.
And on Wednesday, a child at a Southern California elementary school pulled the trigger of a police rifle, firing a bullet that shattered and created shrapnel that injured three youngsters, authorities said.
The AR-15 was locked to the side of a motorcycle on display at Newman Elementary School during an anti-drug programme session when a student managed to fire it, Chino police spokeswoman Tamrin Olden said.