The violence marks the second high-profile mass shooting in the US within three days, after five people were fatally shot and more than a dozen others were injured inside a LGBT+ club in Colorado Springs.
The mass shooting in Chesapeake, Virginia also comes just days after the fatal shooting of three University of Virginia football players.
The Walmart gunman, who was armed with a pistol, was found dead at the scene from an apparent self-inflicted gunshot wound, according to law enforcement officials.
“Tomorrow is Thanksgiving, one of our most cherished holidays that brings us together as Americans and as families, when we hug our loved ones and count our blessings,” the president said in a statement on Wednesday morning.
“But because of yet another horrific and senseless act of violence, there are now even more tables across the country that will have empty seats this Thanksgiving,” he added. “There are now more families who know the worst kind of loss and pain imaginable.”
The president and First Lady Jill Biden “grieve” for the families whose loved ones were killed in the attack, he added. “We also mourn for all those across America who have lost loved ones to these tragic shootings that we must come together as a nation to stand against,” he said.
He pointed to gun reform legislation that was signed into law earlier this year, “but that is not nearly enough,” he said. “We must take greater action.”
The president has repeatedly urged Congress to renew a ban on so-called assault weapons like AR-15-style rifles that have been used in mass acts of violence across the US.
In June, the president signed the Bipartisan Safer Communities Act, which funds programmes to encourage states to adopt so-called “red flag laws” that allow law enforcement to obtain court orders to prevent a person who might pose a threat to themselves or others from obtaining a firearm.
The law also includes a provision to expand federal background checks so that firearms retailers will be obliged to examine the state and local juvenile and mental health records of prospective customers aged 18 to 20.
It also partially closes a so-called “boyfriend” loophole that adds “serious” dating partners who are convicted of domestic abuse to a list of offenders who would not be able to access firearms, and adds their names to the FBI’s National Instant Background Check System.
That law previously only applied to domestic violence offenders who are married, live with, or have a child with a survivor.
Its passage marks the largest gun reform package in Congress since the expiration of the assault-weapons ban in 2004, though it fell significantly short of what the president and Democrats have demanded in recent decades to curb the proliferation of high-powered weapons in the wake of daily mass shootings and school massacres.
There have been more than 600 mass shootings in the US this year, according to advocacy group Gun Violence Archive, which defines mass shootings in which four or people are injured or killed.
Mass shootings have averaged more than one per day. There has not been a single week in 2022 without at least four.
Last year, there were nearly 700 mass shootings, spiking from 610 in 2020 and 417 in 2019. Before that, mass shootings had not surpassed 400 annually since the organisation began tracking such incidents in 2014.