John Hogan, WZZM

GRAND RAPIDS, Mich. — A man in prison for making sexually-explicit videos of children from Grand Rapids to the Upper Peninsula pleaded guilty Monday to sexually assaulting an 18-month-old girl at a Byron Township motel, which police say he recorded it to share with others.

Eric Devin Masters, 29, pleaded guilty to three counts of first-degree criminal sexual conduct during a brief appearance in Kent County Circuit Court.

Investigators learned of the rapes while investigating Masters for sexually exploiting children across the state. He’s already serving a 50-year sentence from that investigation; his older brother is locked up for assaulting a 10-year-old girl.

The former Belding man admitted to assaulting the girl three times over an eight-day period in 2012 at a motel located off U.S. 131 in Byron Township. Detectives were notified of the assaults by an FBI agent investigating Masters for sexually exploiting children in Ionia, Muskegon, Kent, Grand Traverse and Mackinac counties between 2011 and 2013.

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Videos taken at the motel show Masters engaged in multiple sex acts with the girl, who at times was tied to a bed. In one of the videos, Masters is urinating on the child, court records show.

Kent County Circuit Court Judge Mark Trusock accepted guilty pleas on five felony charges. A bespectacled Masters looked down and answered ‘yes sir’ as the judge asked if the facts of each assault was true.

“The parties have entered into a sentencing agreement where the defendant will be sentenced to a 50 year minimum term and that will be concurrent to whatever time he’s doing in the federal system,’’ Kent County Assistant Prosecutor Greg Boer told the judge.

“Your honor, just so we’re clear, this isn’t a cap,’’ he added. “The minimum sentence will be 50 years.’’

“Correct,’’ Trusock responded. “And I will set the maximum.’’

That will happen March 17 when Masters returns to Trusock’s court for sentencing. First-degree criminal sexual conduct is punishable by up to life in prison.

A federal judge in Grand Rapids in March, 2015 sentenced him to 50 years for sexual exploitation of a child. In that case, he admitted to producing sexually explicit material of children and posting it to the Internet.

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One of the videos was made on Christmas, 2011, which is Masters' birthday. Investigators found 21 videos and images depicting sexual exploitation of a child, federal court documents show.

Masters doesn't appear to stay in one place too long; he has addresses listed in several Michigan cities, including Belding and Lowell.

His older brother, 32-year-old Timothy Matthew Masters, was sentenced last fall to 27 years in federal prison for assaulting a 10-year-old girl and then bragging about it to his younger brother.

"Good night last night,'' was the subject line in an Oct. 2013 email Timothy Matthew Masters sent to Eric Masters, which included a pornographic image taken of the victim while the girl slept.

The Kent County brothers traded child pornography and discussed sexual abuse of children with the same nonchalance other brothers might have when discussing a football game.