Will update as info comes in12:50 CST:
Christopher Grey, a spokesman for the Army's Criminal Investigation Division and for the joint task force investigating the crime, said Hasan "has been charged with 13 specifications of premeditated murder under Article 118 of the Uniform Code of Military Justice." He told a news conference that "additional charges may be preferred in the future."
Grey described the murder charges as "the first step in the court martial process" and emphasized that a multi-agency investigation of the Nov. 5 shooting continues. He indicated that investigators have not yet settled on a motive for the massacre.
"We're looking at every reason for this shooting," he said. "We're aggressively following every possible lead."
Grey added: "We still believe that there was only one gunman at the scene involved in the actual shootings." The statement left open the possibility that someone else instigated the attack. Investigators have been examining Hasan's relationship with a radical Muslim prayer leader who formerly served at a Northern Virginia mosque that Hasan attended for a time in 2001. Hasan lived in the Washington area while he was working at Walter Reed Army Medical Center in the District.
Grey said he would not release any details that might jeopardize the investigation or the eventual legal proceedings. But he suggested one argument for premeditation when he told reporters that Hasan did not have any legitimate reason to be at the Soldier Readiness Processing Center last Thursday.
"We do know that the suspect was not at the Readiness Center for any scheduled appointments or command-directed activity," Grey said as he stood with representatives of other agencies investigating the crime, including the FBI and Texas Rangers.
Authorities have said Hasan will be tried in a military court because he is a service member, the shooting took place on an Army post, and all of those slain were Defense Department personnel. Of the 13 who died, four were officers, eight were enlisted soldiers and one was a retired chief warrant officer who was working as a civilian at Fort Hood.
11:48 CST:
An announcement was made Thursday at a press conference at Fort Hood, officials said.
Authorities decided to charge Hasan in a military court, officials said. Additional charges may be filed; however, the murder counts are the most serious of offenses, officials told NBC News.
It was not yet decided whether to charge Hasan with a 14th count of murder related to the death of the unborn child of a pregnant shooting victim.
Military officials can consider the death penalty.
DEVELOPING: Army psychiatrist Major Nidal Hasan will be charged with 13 counts of premeditated murder in last week's Fort Hood mass shootings, NBC News reported Thursday.
Hasan, 39, is suspected of killing 13 of his comrades Nov. 5 when he opened fire at a soldier processing center at the military base in Killeen, Texas.