Now that the initial shock is beginning to wear off, they're starting the grieving process as well as the search for answers at the nation's largest military base.
Sixteen people were injured and three soldiers were killed. The deceased have been identified as Sgt. Danny Ferguson, Sgt. Carlos Lazaney and Sgt. Timothy Owens.
Wednesday's shooting at Texas' Fort Hood left four people dead, 16 injured and thousands struggling to come to grips with how and why this happened -- again.
It was just a few years ago, in 2009, that another soldier opened fire at the base, killing over a dozen people.
While the shooter in that case was found to have clear anti-American views, there's very little known about what led to this week's tragedy.
The gunman has been identified as Army Specialist Ivan Lopez. He served in Iraq, but apparently saw no combat action.
Lieutenant General Mark Milley says Lopez may have gotten in an argument with other soldiers before Wednesday's shooting at the Texas base.
Lopez was being evaluated for post-traumatic stress disorder after serving in Iraq. Milley says there were strong indications that Lopez had an unstable psychological condition.
The family of Ft. Hood shooter Ivan Lopez has released a statement, expressing dismay at the tragic events of this week.
In the press release, written in Spanish, his father is quoted as saying his son could not have been in a good mental state because, referring to the tragedy, he was, "not this way."
He described his son as young and a hard worker, a calm family man. Lopez's father goes on to say in the release that his son was affected by the recent death of his mother and grandfather as well as changes in the military.
He had recently transferred from Ft. Bliss in El Paso.
The Nations Mourns Another Fort Hood Tragedy
House Minority Leader Nancy Pelosi is taking time out to offer condolences to the families of the shooting victims at Fort Hood in Texas.
"For the second time in five years, this community of soldiers, service members, civilians and their families have faced tragedy at their base," she said.
The San Francisco Democrat said the nation's thoughts and prayers are with the Fort Hood community.
"We meet with heavy hearts. Once again, our Army must recover from an act of unspeakable violence here at home," Sen. Carl Levin said.
Levin says lawmakers are meeting with "heavy hearts" after the mass shooting at Fort Hood, Texas. The Michigan Democrat chairs the Senate Armed Services Committee.
He said all available medical and investigative resources are being committed to the aftermath.
Stricter Firearm Regulations
House Speaker John Boehner says individuals with mental illnesses should not be allowed to have firearms.
"Well there's no question that those with mental health issues should be prevented from owning weapons, or being able to purchase weapons. This issue, we need to continue to look at to find a way to keep weapons out of the hands of people who should not have them," he said.
Boehner made the remark in response to a question about the Fort Hood shooting spree.
"And I want the families and first responders to know, we stand with you, we stand by you, and we're praying for you," Boehner said.