The dogs had never been vicious before, the sister said.
A nine-year-old boy was mauled to death by his half-sister's three dogs while she was at work.
Alexandria Griffin-Heady, 24, returned to her trailer in Yuba County, California on Sunday and found the boy, Tyler Trammell Huston, unresponsive, CBS Sacramento reported.
Read: Mom Saw Bloody Dog Before Finding Her Son Mauled to Death: 'He Didn't Cry Out'
Tyler, whose mom passed away in 2011, was in foster care and had been granted overnight visits with his sister, who said she had hoped to adopt him.
Griffin-Heady's lawyer told INSIDE EDITION that she had left the boy alone in the trailer because he was sleeping, and she knew she would only be gone for a couple of hours. But when she returned, she found the tragic scene.
"I failed him," she tearfully told Fox40. "Whether it's my fault, my dogs' fault, whoever's fault. I wanted to protect him and I wanted to give him an amazing life."
Family members say Trammell-Huston was discovered by half sister Ali Griffin-Heady, who wanted to adopt him. pic.twitter.com/ikxdhdfo0U
— Doug Johnson (@DougJohnsonFX40) January 5, 2016
She said the three pit bulls, who appear in multiple videos on her YouTube page, had never been vicious before.
"Never a day in my life," she said.
Tyler was taken to a nearby hospital where he died from his injuries, police said.
The dogs were taken away by Animal Care Services and will be euthanized if they are deemed dangerous.
No arrests have been made. Griffin-Heady's lawyer told INSIDE EDITION that he did not yet know if any charges would be brought against her, but called the incident "an unfortunate tragedy."
"They need to show criminal negligence," Roberto Marquez said. "She knew these dogs well. She raised these dogs. She knew their history. She knew their behavior. She knew everything there was to know about these dogs, and she had no reason to believe this would ever happen."
Read: 15-Year-Old Girl Charged With Murder in the Bloody Killings of Her Mom and Her Mom's Lover
The Sacramento Bee reported that Child Protective Services had allowed Griffin-Head to have her brother for overnight weekend visits.
Following his death, CPS said in a statement that they are "deeply saddened by the tragic death of this child."
"CPS is continuing to work with Yuba County law enforcement during this investigation," it said.
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