PARKER COUNTY, Texas -- A young mother and prosecutors expressed dismay Tuesday upon learning the man held responsible for an infant's death is set to be released from prison after serving only six years of a 20-year sentence.

John Paul Webb, 41, is behind bars for pleading guilty to injury of a child charges related to the 2010 death of his 32-day-old son, Christian.

Angelica Ahern was shocked when she learned just a few days ago that he had been paroled by the Texas Board of Pardons and Paroles last week.

Angelica Ahern looks at a photo of her holding her newborn son.

Although Webb was initially charged with murder, he was never convicted because of issues with the case, which is why prosecutors gave him a plea deal in 2013, according to Parker County Assistant District Attorney Jeff Swain.

"There were some issues with what would have happened if we had gone to trial," Swain said.

Neither he nor Ahern expected Webb to serve a full 20 years, but they both expected substantially more than six.

Parker County Assistant District Attorney Jeff Swain

"We wrote [the board] a letter laying it all out -- why this is a person they need to keep in prison," Swain said. "They have a copy of the full police report and pictures of this baby."

At the time of the incident, Parker County Sheriff Larry Fowler called the injuries to the boy's skull some of the worst he had ever seen.

Ahern admits now that she was abusing drugs and alcohol back then -- which may have impacted the larger case -- but she says now she is clean, and a mother to a little girl and newborn son.

She says that is why is speaking out.

Angelica Ahern

"Maybe they'll realize they're letting the wrong person out," she said.

The Texas Board of Pardons and Paroles reviews these types of cases. A spokesman said further information may be available on Tuesday.

Webb is expected to undergo three months of rehab before being released.

According to the correction department's latest figures, the parole rate right now in Texas is about 35 percent with some 82,000 inmates under consideration annually.