Adams said he then saw a father with his family take out his concealed weapon and shoot the gunman dead.
The man who was shot in the Walmart parking lot after resisting the carjacker was airlifted to a nearby hospital and is in critical condition.
They say they found the 16-year-old's stolen vehicle in the parking lot.
According to authorities, the suspect entered the Walmart Supercenter and opened fire at a display case, without injuring anyone, before leaving the store again to attempt another carjacking in the parking lot.
The gunman then attempted to carjack another vehicle and shot the driver, Wohl and witnesses said.
At least two people have been shot, according to police.
Police say the suspect then tried yet another carjacking in the parking lot, but was approached by two armed civilians.
Shots were fired at the Walmart in Tumwater at about 5pm local time (1am BST), according to reports.
"All of a sudden, you hear this pop or a crash sound.About 15 to 20 seconds maybe even later, another sound exactly the same", said John Gerasimczyk.
"Just drive, please drive", she told the woman. The station reports that as people fled the store, the gunman followed and shots were heard outside.
Kailani Bailey, 19, told the Olympian that she was shopping inside the Walmart when a tall man in a grey t-shirt and jeans ran into the building, pushing past people and shouting "move".
Another witness told KIRO her husband watched the shooter "take his last breath" after being shot by the armed citizen.
"When we got about to the door, I heard someone say, 'gun".
Bailey said she got over to her vehicle, but knew she wouldn't be able to get out of the parking lot because many people were trying to flee. The only facts which seem to not be in dispute are that police were alerted to possible criminal activity in the area when a man with a gun was seen near the Walmart. She was hiding on the ground crying.
"He's a hero", Adams repeatedly called the man. "[.] If this customer hadn't done what he did, I mean - yeah, he's a hero.
She said about that time the neighboring Costco store started evacuating its customers.