Army officials have released few details, citing the continuing investigation. They said Private Santisteban was assigned to the 15th Brigade Support Battalion, Second Brigade Combat Team, First Cavalry Division. The Army’s Criminal Investigation Division said in a statement that the deaths appeared to be the result of a murder-suicide, but that a final determination would not be made until the investigation was complete.

“This is a terrible tragedy for the mother and families of these children,” Maj. Gen. Anthony R. Ierardi, Fort Hood’s senior commander, said in a statement. “We are doing everything possible to care for the family in this time of profound grief and loss.”

It was unclear if anything like it had happened before at Fort Hood involving the spouse of a soldier. Fort Hood officials said they do not have a method to track civilian suicides. In recent years, the focus, both at Fort Hood and throughout the Army, has been on preventing soldier suicides, and very little is known about the suicide rate of Army spouses. Repeated deployments to Iraq and Afghanistan have put a tremendous amount of stress on Army families, as have other problems that affect both military and nonmilitary households, like depression and alcohol abuse.

In January 2010, Deborah Mullen, the wife of Adm. Mike Mullen, then the chairman of the Joint Chiefs of Staff, spoke of the problem of spousal suicide at a military suicide prevention conference in Washington. She said Army leaders told her that they lacked the ability to track suicide attempts by family members of Army personnel because there were too many to track. “I was stunned,” Ms. Mullen said, according to The Associated Press.

At Fort Hood, nearly 70 soldiers have committed suicide since 2009, Army officials said. The base, one of the largest military installations in the world, has an on-post population of about 80,000, including more than 43,000 assigned military personnel. The number of suicides in one year appeared to peak in 2010 with 22. Last year, suicides dropped to five, with two additional cases still unconfirmed and under investigation. Fort Hood officials believe one of the reasons for the decrease has been their focus on behavioral health issues for soldiers and families.