ALBUQUERQUE, N.M. (KRQE) — A former Sandia National Laboratories subcontractor was sentenced to more than three and a half years in prison. The subcontractor, Bobby Peña, was charged with bilking the lab for thousands of dollars and for possessing child pornography.

Federal prosecutors charged Peña with defrauding the U.S. Department of Energy (and thereby the labs) 28 individual times, submitting invoices for work he didn’t perform. The invoices, dated between July 2015 and November 2016, accounted for $6,000 for cleanroom cleaning services and $47,025 for air monitoring services that allegedly hadn’t been performed, according to the federal indictment and plea agreement.

Peña was paid more than $70,000 via fraudulent invoices, according to his guilty plea. And on top of that, while in the process of gathering evidence for the case, law enforcement found child pornography on hard drives at Peña’s business address.

In total, they found nearly 4,000 images and 58 videos showing children engaged in sexual activity, according to the U.S. Attorney’s Office, which prosecuted the case. Some of the files dated back to 2008. Presented with the evidence, Peña pled guilty to the fraudulent invoices and a single offense related to downloading and storing child pornography, according to plea documents from federal court.

He was sentenced on Monday to three years and seven months in prison. Because he “demonstrated acceptance of responsibility for this [child pornography] offense,” his sentence was lightened slightly, according to court documents.

Once he’s out, Peña will be subject to five years of supervision and must register as a sex offender. He also has to pay back the money he took from the U.S. Department of Energy and pay $15,000 in restitution to five victims.