LAKE FOREST – Terrified, 6-year-old Anna Cooper curled into a ball. Still, the brown and white boxer came at her.

He bit Anna’s face, her shoulder and several areas on her left leg. The girl screamed. Watch video here.

Her brother Steven, 14, heard the screams and ran to help. He beat the dog over the head with closed fists. Anna’s sister Grace, 3, ran to next-door neighbor Lisa Horner, who came out with Windex and rose clippers.

The dog biting, Anna screaming, siblings and neighbors rushing to save her; it upended this tranquil Lake Forest neighborhood near El Toro and Trabuco roads on Wednesday. And it brought Jennifer Cooper, Anna’s mother, running from the family room.

Cooper, 43, home schools her children: in addition to Steven, Anna and Grace, there is Matthew, 12, Nathan, 8, and Gabriel, 14 months. Cooper and her son Steven were going over lesson plans for speech, debate and piano when the dog attacked. Anna’s shrieking got everyone’s attention.

“It was a mother’s worst nightmare, seeing my child being harmed,” Cooper said. “I kicked (the dog), but he kept coming back and attacking my daughter. Finally, I pulled Anna from the dog. I started yelling ‘bad dog’ and ‘go home,’ but he was so aggressive he wasn’t leaving. The rest of my children were out, and I carried Anna back with blood running down her legs. He came at my baby, bit his pant leg and then stood over him.”

Steven was the last one in. He walked backward to the front door – afraid to turn his back – as the dog continued to show aggression.

Once inside Cooper checked on Anna and Gabriel. They were crying but seemed stable otherwise. She said she thought about calling 911, but said she was worried about other children in the area.

Cooper ran to an upstairs bedroom, where she and her husband have a gun safe. Cooper pulled out a Glock 19 loaded with 9 mm Hornady hollow-point ammunition, cocked it while running down the stairs and went to the door.

“I looked out my peep hole, and the dog was still there, standing 20 feet from my door,” said Cooper, who was raised on an Oregon farm around animals and guns. “I made sure there were no people out there in the cul-de-sac, I pulled the door open and aimed at the dog’s chest and shot him.

“Dogs are so tough and vicious. I was afraid of it running down the street and attacking another person. I knew the only way to stop him was the gun. My only regret is that I wasn’t able to kill the dog,” she said.

The dog did die of its wounds Thursday, said Ryan Drabek, interim director of OC Animal Care.

He said the dog was not automatically euthanized because “it is somebody’s animal. If it is deemed treatable, we have to provide the best care possible.”

The animal – officials are considering it a stray dog; the owner has not been located – will be tested for rabies and a necropsy will be performed as part of an investigation into the incident by the Orange County Sheriff’s Department, Drabek said.

The lesson Cooper wants for her children is that they know they are safe in their own home.

“I want them to know that Mom is just a step away, and I’ll be there to protect them,” she said.

No need to prove that to Anna, who was doing better Thursday, although she said she’s afraid of all dogs now except puppies and Chihuahuas.

“My mom is really brave,” she said.

Contact the writer: 949-454-7307 or eritchie@ocregister.com