Nathaniel Grant, Kazeem Kolawole and Anthony McCalla were convicted by a jury at the Old Bailey of causing grievous bodily harm to Thusha Kamaleswaran.
She was gunned down as she played in her aunt's shop in south London in March last year.
A bullet hit her in the chest and passed through the seventh vertebra of her spine, leaving her wheelchair-bound for life.
Shopper Roshan Selvakumar was shot in the face in the attack, and has been left with bullet fragments permanently lodged in his head.
Grant, Kolawole and McCalla were looking for a rival gang member when Grant mindlessly opened fire into the Stockwell Food and Wine shop.
Jurors were told that he would have been able to see Thusha as he fired his second shot.
They were shown dramatic CCTV footage from inside the store, where Mr Selvakumar can be seen with blood pouring from his head and Thusha lies slumped on the floor.
Today the three defendants were found guilty of causing grievous bodily harm with intent to Thusha, now six, and Mr Selvakumar.
They were also convicted of attempted murder of their intended victim Roshaun Bryan.
The two innocent bystanders injured in the shooting were lucky to survive.
Thusha went into cardiac arrest twice and had to undergo emergency surgery, both in the shop and in hospital to save her life.
If Mr Selvakumar's injury had been slightly to one side, he would have died.
Police spent hundreds of hours scouring CCTV footage to track down the three gunmen.
They had links to the Brixton-based OC gang, which had a rivalry with ABM, based in Stockwell.
Prosecutor Edward Brown QC told jurors: "The reality of this shooting may be that, whilst there was an intention to kill the suspected rival gang member, the gunman and his accomplices couldn't have cared less if someone else was shot too."