Story highlights David Gatlin, Joseph Ozment, Charles Hooker and Anthony McCray are released

All were serving life sentences in murder cases

The four served as trusties at the governor's mansion during Haley Barbour's term

Families of the victims express outrage at the pardons

In his last days in office, outgoing Mississippi Gov. Haley Barbour pardoned four men convicted of murder, a state official said Monday.

David Gatlin, Joseph Ozment, Charles Hooker and Anthony McCray received full pardons and were released at 1 p.m. Sunday, said Suzanne Singletary, spokeswoman for the Mississippi Department of Corrections. All four were serving life sentences and worked as trusties at the governor's mansion, she said.

"It is at any governor's discretion," said Singletary.

Gatlin was convicted of murder, aggravated assault and burglary of a residence, she said. Ozment was convicted of murder, conspiracy and armed robbery in a separate case. Both inmates were at minimum security level, she said.

Hooker was convicted in a 1991 murder, while McCray was convicted in a 2001 murder, Singletary said. The governor also recently pardoned Nathan Kern, who was serving a life sentence for burglary, she said.

Families of the men's victims told CNN affiliates WAPT and WLBT they are outraged by Barbour's decision.

JUST WATCHED Four convicted killers pardoned Replay More Videos ... MUST WATCH Four convicted killers pardoned 03:18

Attempts by CNN on Monday to reach Barbour's office for comment on the pardons were unsuccessful.

In 1993, WLBT reported, Gatlin walked into the trailer where his estranged wife, Tammy Ellis Gatlin, lived and shot her in the head. The woman's friend, Randy Walker, survived a gunshot to the head.

"Is Gov. Barbour going to pardon us from our aches and pains and heartache that we have to suffer?" the victim's mother, Betty Ellis, asked WLBT. "Is he going to pardon a child that had to grow up without a mother? Is he going to pardon me from never being able to feel her arms around my neck again? What is Barbour going to do about that?"

Tammy Gatlin's sister, Tiffany Ellis Brewer, said David Gatlin served less time than her sister lived.

"It's completely unfair," she said. "I mean, he's in jail for 18 years. She was 20 years old when she died and had her child laying in her arms when he shot her in the head. And he's pardoned?"

David Ruth, who was the lead investigator on the case, said there was an apparent communications foul-up. Tammy Gatlin's relatives received a letter from the state parole board Friday saying David Gatlin was not going to be paroled and would next be considered in October 2012. They received a call the next day saying he was being pardoned, Ruth told WLBT.

Meanwhile, the family of Ricky Montgomery told WAPT they received a call from the department on Saturday reporting Ozment's pardon. Montgomery, 33, was a store clerk who was slain on the job. Ozment was convicted of his murder.

"Of course it's devastating," said Mark McAbee, Montgomery's nephew. "You know, we go through this and it's reliving it over and over again, when I don't think the general public has any idea of the things these convicts are doing."

McAbee said his mother was incredulous two years ago to learn Ozment had been assigned to work at the governor's mansion. She wrote the Department of Corrections, he said, which told her that he met the requirements and underwent a screening process.

"We have people out on the streets that are sex offenders that have to register," McAbbe said. "This is a man (who) killed somebody. This man took somebody's life, and it's not going to indicate that on any paperwork."

Phil Bryant, Barbour's successor, is set to be inaugurated on Tuesday.