The jury had to decide between charges of either capital murder or reckless manslaughter, with McLellan's intent being the difference between the two.
A reckless murder charge would indicate the jury believed he acted recklessly when he fired the gun, and a capital murder charge would indicated he intended to kill Sherri William's brother, but struck her instead.
The jury deliberated for about four hours before convicting McLellan of capital murder.
"He shouldn't have been shooting. There's no doubt about that," McLellan's attorney Erskine Mathis said in court.
"This was an absolute accident. He didn't even know that girl was in the world and if you look at those photographs that were still shots from the videos that were made, even from the ones showing from his back when he's firing the bullet, firing the gun, you can't see her down there," Mathis added.
Assistant District Attorney Mara Russell said she believes the conviction is justice for Sherri.
"I also want to say that it was because of the citizens in the community came forward with what they knew and what they had, that was very helpful," Russell said.
Even though McLellan is charged with capital murder, he will not face the death penalty. He will be sentenced to life without the possibility of parole on October 3.
McLellan did not show any reaction as the verdict was read on Thursday morning. We will have reaction from his family members on FOX6 News at 5 p.m. and 6 p.m.