A shooting at a military base in Texas state left four people dead, including the gunman, and at least 16 wounded on Wednesday evening, according to US authorities.
The gunman, who was reportedly acting alone, was identified as Ivan Lopez, an Iraq war veteran. Authorities said he was struggling with mental health issues.
He was in uniform at the time of the incident, authorities said. Lopez used a .45 caliber Smith & Wesson semi-automatic handgun he had bought recently.
He opened fire at two separate locations. When confronted by a female police officer, he first put up his hands. But pulled out a gun from under his jacket and shot himself in the head.
The base, called Fort Hood, had witnessed a massacre in 2009 when a US army psychiatrist Major Nidal Hasan killed 13 people, all but one were military personnel.
Watch: Mass shooting at Fort Hood army base in Texas
Law enforcement said the two shooting were not connected.
Doctors at a hospital treating the wounded on Wednesday said their conditions ranged from "stable to quite critical". Two more injured were on the way at the time of reporting.
President Barack Obama, who was in Chicago for political events, said, "Obviously this reopens the pain of what happened at Fort Hood five years ago."
"We're heartbroken that something like this might have happened again," he added.
The 2009 gunman, Hasan, refused to defend himself at his trial and owned up the killings saying he wanted to prevent those military personnel from deploying to Afghanistan.
During his trial, witnesses said he targeted soldiers as he walked through the building shooting. He stopped when he was shot in the back, that left him paralyzed below the waist.
He was found guilty and sentenced to death.
In another shooting on a US military facility, a former US navy man opened fire at Washington DC naval yard killing 12 people last September, before he was shot dead by a police officer.
Indian American Vishnu Pandit, a 61-year-old navy engineer, was among gunman Aaron Alexis’s 12 victims. He came to the US from Mumbai in the mid 1970s.