YULEE, Fla. -

A father found guilty in the death of his baby was sentenced Thursday to eight years in prison followed by eight years of probation.

The judge heard emotional testimony earlier this month in the sentencing of Robert Jerrell, 35, who was convicted in December of aggravated manslaughter for leaving his 9-month-old son alone in a bathtub at their Callahan home in May 2012. The boy drowned.

The sentence he handed down was below the standard guidelines, according to the state attorney's office.

Jerrell told the judge what happened to his son was the biggest mistake of his life and he would always carry it with him.

Robert Jerrell

His statement that day came after about an hour and a half of testimony from family members, all of whom talked about how good of a father Jerrell was to his son Aaron (pictured below). They pleaded to the judge to not leave Jerrell's other 3-year-old son without a father.

Jerrell's wife and mother of the baby called his death a "terrible mistake," telling the judge Jerrell's other son "needs his father."

Jerrell was at home with the baby and his then-2-year-old son when he put both in a bathtub filled with water. After a period of time, Jerrell took the 2-year-old out but left his 9-month-old son in the tub unsupervised, long enough that he drowned.

The baby's grandmother said it wasn't intentional.

Aaron Jerrell

Jerrell said he went to find a gas can for his brother and when he came back it was too late.

The state countered, saying the jury found Jerrell to be negligent, bringing up his issues with substance abuse. Prosecutors also brought up Jerrell's failure to complete the Department of Children and Families programs needed to see his 3-year-old son.

Sentencing guidelines suggested 13 years in prison for Jerrell. The prosecution asked the judge for 25 years, saying Jerrell is a habitual felony offender.

But the defense said this was an isolated incident and asked for probation with some kind of drug rehabilitation that would allow him to return to his family.