Robert Gee, 34, of Marengo.

A Marengo man was sentenced to the minimum sentence of 3 years in prison for shaking his 10-week-old son, causing his death, prosecutors said.

Robert Gee, 34, of the 600 block of West Prairie Street in Marengo, was charged with involuntary manslaughter on March 30, 2012.

The Boone County State’s Attorney’s Office said that Gee was found guilty by Judge C. Robert Tobin III following a two-day bench trial that ended on Monday.

Witnesses testified that Gee admitted to shaking his infant son, causing the child’s death, according to prosecutors.

Prosecutors did not release any additional details of the incident, which occurred on May 23, 2011. The case was investigated by the Belvidere Police Department.

Tobin sentenced Gee to three years in the Illinois Department of Corrections on Thursday.

Involuntary manslaughter is a Class 2 felony with a statutory range of 3-14 in prison. Under truth-in-sentencing guidelines, Gee must serve at least 50% of his sentence.

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He will be required to undergo two years of mandatory supervised release once he is out of prison.

Gee must also register with the violent offender against youth registry.