Kim Schwieters told the newspaper she saw armed police running into the department store and her daughter spotted people lying on the ground before police told shoppers to clear the area.
At least three people were wounded in the attack, which is being described by police as "an interrupted theft".
The second victim, who was believed to be a family member or friend of the other victim, was stabbed after intervening.
Two other people that were with the victim ran to help, and confronted the suspect.
CBS reported Abdirahaman sneaking into a men's fitting room at the Mall of America, Minneapolis outlet and attempting to steal something from a customer's belongings while the man was outside the fitting room modeling clothes for his family.
Twitter reports said one suspect was arrested. "Kind of drew attention to himself".
One woman tweeted: "Just lived through the scariest experience of my life".
The incident took place near where shocked shoppers were lining up to see Santa Claus. He got me!'. I knew something was not right.