On June 30 in Mexico, 22 people were killed by the Mexican Army in what soldiers said was a gun battle. Right after the incident, politicians praised the Army for its actions.

In the months since, questions have surfaced over the so-called shootout. A witness instead has described it as a massacre and evidence doesn't indicate a gun battle between soldiers and criminals, The Los Angeles Times reported.

Mexican President Enrique Pena Nieto said that all of those questions will be answered in an investigation by the attorney general.

"The attorney general is digging into the investigation and will be the agency responding to this issue," Pena Nieto told the Associated Press.

A witness told the media that Mexican soldiers killed the 22 people after they had surrendered. There had been a brief fight between soldiers and the people in a warehouse in the town of San Pedro Limon prior to the surrender.

The witness, who asked not to be identified, said the men walked out of the warehouse with their hands on the back of their necks before they were killed. Blood splatter on the walls of the warehouse and a lack of shell casings seem to indicate methodical killing, rather than a gun fight.

At the time of the incident, the Mexican army said they were fired upon by an armed gang at the warehouse and they returned fire to defend themselves, killing 22 people in the exchange. Only one soldier was wounded.

The Mexican army continues to stand by its original account of events.

Pena Nieto's announcement on Tuesday came four days after the attorney general said the incident would be placed under investigation. Mexico's National Commission on Human Rights is conducting an independent investigation.

The U.S. State Department said Friday that it is "imperative that there is a credible review of the circumstances," and strongly encouraged Mexico to investigate the confrontation.