There are airsoft (plastic BB) guns out there that are convincing replicas of real firearms, and a little doctoring to remove the orange ends renders them a convincing facsimile of the real thing--especially at a distance, especially pumped with adrenalin from getting a call of 'man with a gun'.
I would have to see the item in question before I could make a call of a foul shoot, and it would have to be obviously NOT a weapon. (and that's not going into people who might paint the tips of their weapons orange to make them look like toys).
According to the article, the “Deputy Chief of Field Operations” “said the child did not threaten the officer verbally or physically.” If the quote is correct, it doesn’t look good.
Did the boy lift the BB pistol to point it at anyone else? Did something else happen? Were other people in the area only standing around or looking nervous or getting away? Who knows? But it doesn’t look good.