Kenosha, Wis. — A 45-year-old Kenosha man has been charged with a series of sex crimes, including the repeated sexual assault of a child and possession of child pornography. Matthew H. Nielson was formally charged today and could face up to 335 years in prison if convicted.

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Nielson appeared in court today, where he was ordered to be held on a $200,000 cash bail. The charges against him include repeated sexual assault of a child, child enticement, and ten counts of possession of child pornography.

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Details of the Investigation

According to the criminal complaint, the investigation began when the FBI received an anonymous tip in June 2024. The tipster reported that years ago, they had discovered explicit images of a young girl, later identified as “Emily”, on Nielson’s computer. The victim, now an adult, came forward and confirmed the abuse she suffered as a child.

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The FBI and Kenosha County Sheriff’s Office launched a joint investigation, which included reviewing past reports and conducting interviews with witnesses. Authorities identified additional potential victims and gathered evidence from Nielson’s past residences.

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Arrest and Search Warrants

On February 17, 2025, Nielson was arrested in La Crosse, WI, after authorities tracked his movements through GPS and cell phone location data. He was found sleeping in his vehicle outside a train yard. A search of his vehicles yielded multiple electronic devices, including hard drives, SD cards, flash drives, and a laptop.

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A subsequent search of Nielson’s residence in Kenosha uncovered a trove of disturbing materials, including extensive child sexual abuse material (CSAM). Investigators found thousands of files, including images and videos of children in explicit situations. Some files appeared to be secretly recorded at public locations such as water parks and beaches.

Community Concerns and Law Enforcement Response

The criminal complaint describes years of concerning behavior by Nielson, including interactions with neighborhood children and a history of inappropriate conduct. Witnesses recalled incidents where Nielson spent excessive time with young children, took inappropriate photos, and engaged in other suspicious activities.

Authorities have urged any additional victims or witnesses to come forward as they continue to examine the vast amount of digital evidence recovered.

Next Steps in the Case

Nielson remains in custody at the Kenosha County Jail. His next court appearance is scheduled for later this month, where prosecutors will present further evidence. If convicted on all charges, he faces a potential maximum sentence of 335 years in prison.