Washington (CNN) How a man who was discharged from the US Air Force for assaulting his spouse and child was able to purchase the firearms he used to carry out the deadliest shooting rampage in Texas history is just one of many questions facing investigators as they continue to look for answers on Sunday's church massacre that left 26 people dead.

On Monday the Air Force acknowledged it did not relay the killer's court martial conviction for domestic assault to civilian law enforcement that could have prevented him purchasing the firearms used in the shooting.

The gunman in Sunday's shooting has been identified as 26-year-old Devin Patrick Kelley , according to law enforcement officials. As a member of the US Air Force, Kelley served in logistics readiness at Holloman Air Force Base in New Mexico starting in 2010.

Kelley was court-martialed in 2012 for two counts of Article 128 of the Uniform Code of Military Justice, assault on his spouse and assault on their child, spokeswoman Ann Stefanek said Monday. Kelley received a bad conduct discharge, confinement for 12 months and a reduction in rank, she said.

The Air Force did not provide a date of the discharge, but his military record indicates he left the service in May 2014.

"Initial information indicates that Kelley's domestic violence offense was not entered into the National Criminal Information Center database by the Holloman Air Force Base Office of Special Investigations," an Air Force statement issued later Monday said.

The failure to relay the information prevented the entry of his conviction into the federal database that must be checked before someone is able to purchase a firearm. Had his information been in the database, it should have prevented gun sales to Kelley.

Kelley's background

The man who opened fire at First Baptist Church in Sutherland Springs had previously faced multiple charges in his 2012 court-martial related to violations of the Uniform Code of Military Justice, including several involving firearms, according to records released by the Air Force.

He was originally charged with assault and battery against his wife, aggravated assault against his step-son and four charges involving firearms -- including two charges of pointing a loaded firearm at his wife and two charges of pointing an unloaded firearm.

The firearms charges were dropped prior to trial as a result of a plea agreement. Kelley pleaded guilty to aggravated assault against the child and assault against his wife.

Here is what he pleaded guilty to:

Assault against a child: Kelley assaulted a child under the age of 16 "striking him" on the "head and body" "with a force likely to produce death or grievous bodily harm."

Assault against his wife: Kelley struck his wife with his hands, kicking her, choking and pulling her hair.

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But despite his history of domestic abuse and questionable behavior involving firearms, Kelley was able to purchase the Ruger AR-556 rifle he allegedly used in the shooting from a store in San Antonio, Texas in April 2016, a law enforcement official said.

There was no disqualifying information in the background check conducted as required for the purchase, a law enforcement official told CNN.

At one point, the shooter tried to get a license to carry a gun in Texas but was denied by the state, Texas Gov. Greg Abbott said, citing the director of Texas' Department of Public Safety.

"So how was it that he was able to get a gun? By all the facts that we seem to know, he was not supposed to have access to a gun," Abbott told CNN. "So how did this happen?"

Planned reviews

The Air Force Inspector General is currently conducting an investigation into what happened. The Pentagon has also requested that its own inspector general review the handling of Kelley's records, along with the Air Force, as well as its reporting practices more broadly.

"The DoD IG will also review relevant policies and procedures to ensure records from other cases across DoD have been reported correctly," said Mark Wright, acting deputy director of defense press operations.

Consistent with the Air Force statement issued Monday, a federal law enforcement official told CNN that federal authorities have found no records they were notified of the conviction.

Federal law prohibits individuals convicted of a misdemeanor crime involving domestic violence from owning firearms. The military is required to report domestic violence convictions to civilian law enforcement.

Classifying Kelley's discharge as "bad conduct" rather than as "dishonorable" also raises an important distinction when it comes to the question of how he was able to purchase the firearms used in the shooting.

A dishonorable discharge is considered the most severe classification of punitive military judgments and US federal law prohibits ownership of firearms by those who have been dishonorably discharged.

A bad conduct discharge is considered slightly less severe and does not implicitly block individuals from obtaining or possessing guns.

On Monday, ATF Special Agent in Charge Fred Milanowski addressed media questions regarding Kelley's ability to purchase firearms with his previous discharge from the military.

"In general, if an individual has a dishonorable discharge from the military they would be prohibited from possessing or purchasing firearms and this specific investigation we are early in the investigation, we do not have all the documentation yet. Until we can get all the documentation to determine exactly what his discharge and conviction in the military we will not have a determination on if this individual was prohibited from possessing or purchasing firearms," he said.

Classification

While the ATF was careful to say that they have not received all the documentation related to Kelley's discharge, the specific classification of his release from the military could provide clues into how he was able to obtain the firearms.

It is known that Kelley was confined for 12 months following a 2012 court-martial that found him guilty of two counts of assault involving his spouse and child.

And the nature of those crimes is raising questions around how he was able to purchase the AR-556 rifle just four years later, despite federal law that prohibits individuals convicted of a misdemeanor crime involving domestic violence from owning firearms.

"This is true whether or not the statute specifically defines the offense as a domestic violence misdemeanor. For example, a person convicted of misdemeanor assault against his or her spouse would be prohibited from receiving or possessing firearms," according to a provision in the Federal Gun Act of 1968.

And the fact that his conviction carried a penalty of 12 months confinement should have also prevented him from buying a gun, according to ATF regulations

"What is so beguiling is you are clearly prohibited from owning a firearm just as if you are a convicted felon or denounce your US citizenship," legal analyst James Gagliano told CNN's John King on Monday. "You have a misdemeanor conviction where there was violence detached to members of your family ... that happened in the court martial," he added, noting Kelley spent a year in confinement for his conviction.

Gagliano also echoed Abbott's questions over Kelley's ability to purchase a gun even though he was denied a license to carry it.

"It is utterly baffling and unconscionable that someone can own a weapon and not be allowed to carry it," he said. "Remember, in Texas, to have an open carry privileged you have to have a concealed carry permit. Not every state requires that but Texas does."

Kelley is accused of killing 26 people, including the 14-year-old daughter of the church's pastor, and injuring more.