More info in the article:
"One of Penley's classmates said he, too, thought the gun was real -- and that Penley was going to kill him -- until he grabbed the pistol and realized it was fake. "
...
"'"He started to point the gun at me, so I started to grab for it and he pulled it away,' Cotey told WKMG. 'And then I grabbed for it one more time 'cause he pointed it at me for like a little while, so I grabbed it and I twisted it and I pointed it at him.'
"It was then that Cotey knew for sure the gun was a fake. (Watch Cotey describe the frightening ordeal -- 1:33)
" 'While I was twisting it, it started to come apart like a toy gun would, like a dollar-store type toy,' he said."
...
Authorities pleaded with the boy inside the bathroom to put down his weapon, Eslinger said, but the boy refused.
"'He refused to even comment. All he said was his first name. He did not drop the firearm,' the sheriff said.
"Finally, the boy came out of the bathroom and 'raised the firearm in a tactical position and pointed it' at a SWAT team member, who 'decided to use deadly force,' Eslinger said."