A 24-year-old Louisiana man was sentenced to 30 years in prison after pleading guilty to sexually abusing a four-year-old girl. William Harvey Watson also pleaded guilty to possessing and producing child pornography.

Watson will spend 30 years behind bars on a charge of sexual battery of a victim under the age of 13, as well as 25 years each for each charge of the 250 counts of possession of child pornography and 27 counts of production of child pornography of children under the age of 13, according to PX11.

The St Tammany Parish District Attorney's Office said all sentences will be served concurrently.

Watson was reportedly briefly left in charge of the 4-year-old girl in February 2017. When the girl's mother returned, the door was locked and it took the man some time to open it.

When she was allowed in, she noticed her daughter's clothing was disheveled and inside out, the district attorney's office said. The girl's mother spoke to her daughter, who told her what Watson had done, the district attorney's office said.

The mother told police and Watson was arrested.

The St Tammany Parish Sheriff's Office obtained a search warrant for his home and electronic devices. According to PIX11, Watson admitted to touching the girl and taking sexually explicit photos. He also told officers that he had a sexually transmitted disease.

Investigators found 473 photos and 10 videos of pornography involving children under the age of 13 when searching Watson's computers.

Most of the victims were under the age of five, including an eight-month-old baby. The Times-Picayune reported Watson admitted to police that he got in trouble years ago for sexually abusing an 18-month-old girl in Texas.

The majority of the children were on the National Center for Missing and Exploited Children's database.

According to the district attorney's office, Watson told authorities he was sexually attracted to children and that he downloaded the photos and videos to "satisfy those urges".

Assistant District Attorney Blair Alford has filed a motion seeking to increase Watson's sentence. The victim's family has submitted a request that Watson face the maximum sentence allowed under law of 99 years.