Tragic Audrii Cunningham's mom posts heart-wrenching message that 'she failed her daughter' as her cops find her body in a river and arrest dad's swastika-tattooed friend Don Steven McDougal who lived at his house

The mother of Audrii Cunningham, the 11-year-old who was found dead in a Texas river on Tuesday night, nearly a week after she was reported missing, admitted in a tragic Facebook post that she had 'failed her daughter.'

Cassie Matthews posted the message before her daughter's body was found in the Trinity River, around 10 miles from where the child lived with her father, grandparents and other family members.

Police are preparing murder charges against 'family friend,' a Nazi tattoo having career criminal named Don Steven McDougal, who lives on her father's property in a trailer.

McDougal had taken Cunningham to the bus stop in the past or would take her to school if she missed the bus, officials said. 

Matthews lashed out in her posting at online rumors that she lost custody of her daughter because of a failed drug test. The grieving mother said that was a rumor spread by her child's father. 

'I'll make this clear one time and one time only, I failed my daughter by being bullied into submission by her fathers family and being made to believe she was in a safe, loving, and normal home with her father,' she wrote in a follow-up post. 

Cunningham's father, Joshua, pictured with the man accused of killing his daughter, Don Steven McDougal. The suspect's swastika and SS tattoos are clearly visible on his left arm

Audrii’s family had reported her missing on Thursday after she failed to return after school to her home in Livingston

The girl's mother, Cassie Matthews, pleaded for help from the public during the six-day search for her daughter, and wept as she said the loss had her feeling 'empty' 

Pictured: A chilling mugshot of McDougal, the last person to see the youngster alive, according to police  

In other sometimes rambling Facebook posts, Matthews said she never 'chose drugs' over her child or that she took drugs in front of her. 

Matthews said that she has 'nothing to hide' as she accuses of people of 'spreading bulls***' online. 

'The most important and only important thing to me is finding my daughter! I could give a fuck less what everyone thinks. What you think and your judgement isn't giving my daughter back.'

Matthews references McDougal saying 'if your speculation was true I'd be sitting in the same boat as the man who has taken my baby from the family that loves her.'

In a later message, Matthews reiterates that she never lost custody of her daughter. 

'That is my daughter and I never lost any rights to her so as her parent I’m going to involve myself in anything I please concerning my child! I’m tired of all the bull**** and I’m tired of being silent, scared, and once again bullied into submission by people I don’t f***ing know,' she wrote.

Polk County District Attorney Shelly Sitton has confirmed that charges of capital murder are being prepared against McDougal, 42, Sitton did not say if it will become a death penalty case. 

Lyons said there is 'substantial evidence' in the case, and that cell phone data and videos helped identify places to search. He added that the Trinity River Authority lowered water levels on the river, which led to the discovery of her body.

Audrii Cunningham's body was found Tuesday in the Trinity River near US-59, Polk County Sheriff Byron Lyons announced. 'My heart aches with this news and I express with my deepest sympathy and condolences to everyone who knew, who cared for, and loved Audrii,' Lyons said

Sheriff Lyons said there is 'substantial evidence' in the case, and that cell phone data and videos helped identify places to search

The sheriff also said that the Trinity River Authority lowered water levels on the river, which led to the discovery of her body

The search for little Audrii Cunningham lasted for five days before coming to a tragic end on Tuesday night 

McDougal had allegedly walked Audrii to school on the morning she vanished 

McDougal has a criminal history dating back to 2001 that includes convictions on two counts of enticement of a child

Audrii sparked a state-wide search after she vanished early Thursday morning in Livington, around an hour north of Houston, when she didn't turn up for school 

As authorities investigated Audrii’s disappearance last week, they had named McDougal as a person of interest and he was arrested Friday on an unrelated assault charge 

Court records from Brazoria County, south of Houston, show McDougal pleaded no contest to two felony counts of enticing a child stemming from a 2007 incident and was sentenced to two years in prison. 

The sheriff said that the girl’s body has been taken to the Harris County medical examiner’s office in Houston to determine the cause of death.

Audrii’s family had reported her missing on Thursday after she failed to return after school to her home in Livingston. After she was reported missing, investigators discovered that she never got on the bus to go to school that morning. 

A backpack that authorities believe belonged to the child was found Friday near the dam on Lake Livingston, one of the state’s largest lakes.

As authorities investigated Audrii’s disappearance last week, they had named McDougal as a person of interest and he was arrested Friday on an unrelated assault charge.

When the search was still ongoing, the girl's mother pleaded for help from the public and said it was not like her daughter to just run off or disappear. 

'We have no leads so we are grasping at any string, any signs, anything in general,' she told KPRC at the time. 

'There is not one feeling you feel,' she explained. 'You are broken, you are mad, you are empty and right now I am empty. 

'I am not going to be the same unless my baby is returned to me and neither is her family, any of us, any of her friends, any of the people that she has been connected to in the community.'

The desperate search sparked fervent speculation online and drew in multiple law enforcement agencies, as a statewide Amber Alert was raised. 

Police began searching the wooded area near the young girl's home as she is a lover of wildlife and nature, her family said. 

It was determined shortly into the search that the disappearance was not an accident, as Lieutenant Craig Cummings said at a press conference that 'based on the evidence that we've got we understand foul play is a factor.'