Few details were immediately available about what led to the gunfire at Fort Stewart in the state of Georgia, but officials said the shooter was Sergeant Quornelius Radford, 28, who used a personal handgun, not a military firearm.
Radford opened fire where he worked but officials wouldn't speculate about a motive, authorities said.
The injured soldiers are stable and expected to recover, said Brigadier General John Lubas. The soldiers who tackled Radford helped ensure his arrest, said Lubas.
"These soldiers, without a doubt, prevented further casualties or wounded," he said.
This latest act of violence on a US military installation - sites that are supposed to be among the most secure in the country - again raised concerns about safety and security within the armed forces' own walls.
The US Army said it's investigating the shooting. There were still many unanswered questions, including the scope of the injuries and the shooter's motive.
The injured were taken to the hospital and three underwent surgery, officials said.
Army records show Radford enlisted in January 2018. He worked as a supply sergeant and has not been deployed.
Law enforcement was sent to the 2nd Armoured Brigade Combat Team complex shortly before 11am on Wednesday, local time and the shooter was arrested shortly after, officials said.
The lockdown lasted about an hour. After it was lifted, cars began to move through the normal security checkpoint at the fort's main gate.
Fort Stewart is the largest US Army post east of the Mississippi River by land area and is home to thousands of soldiers.
US President Donald Trump called the shooter a "horrible person" in comments to reporters at the White House.
The FBI was at the fort to help investigate, said Deputy Director Dan Bongino.
Among the deadliest acts of violence on US military bases was in 2009 when a US Army psychiatrist killed 13 people in a shooting that left more than 30 wounded at Fort Hood, a military installation in Texas.
In 2013, a defence contract worker and former navy reservist killed 12 people at Washington Navy Yard. He was then killed in a gun battle with police.
In 2014, a soldier opened fire on his fellow service members at Fort Hood, killing three people and wounding more than a dozen others before the gunman killed himself.
In 2019, an aviation student opened fire in a classroom at Naval Air Station Pensacola in Florida, killing three people and injuring another dozen people including two sheriff's deputies.
Just days earlier, a US Navy sailor shot two people to death before killing himself at Pearl Harbour, the Naval station in Hawaii.
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