The victim was an employee who has life-threatening injuries.
Police say a suspect was detained.
Investigators haven't given an update since shortly after the incident but said they couldn't confirm an arrest or a motive.
"It was a knife type object. The victim was stabbed a couple of times in the back. In the neck area," said Lt. Mark Moreno.
Outside the bakery, ABC7 News talked with a man who said he saw the attack occur.
He wished to remain anonymous.
"The lady finally screaming ran out from the counter and fell down on the coffee machine and her eyes closed," he said.
MORE: BART employee wounded inside station; no arrests made, spokesperson says
BART worker wounded inside station; no arrests made: Spokesperson
News of the stabbing stunned the local community.
The bakery is one of the most popular places to eat for both residents and visitors alike.
"It's one of the go-to stops in Chinatown. It's actually one of the go-to bakeries in all of San Francisco," said Lily Ho of the Delta Chinatown Initiative.
Chinatown has been one of the city neighborhoods hit hardest by the pandemic.
Now, local leaders are hoping this attack doesn't undo any of the recent progress made bringing people back out to the area.
"The whole community has been working so hard for years to bring foot traffic back into the community to make people feel welcome, to make people feel safe," Ho said.
MORE: San Francisco mayor announces budget proposal prioritizing public safety
SF mayor wants to increase budget for public safety
Supervisor Aaron Peskin - whose district includes Chinatown - says his office is in contact with the shop's owner to offer support.
If you have information on the stabbing, contact the SFPD at 415-575-4444 or text a tip to TIP411 and begin the message with SFPD.
If you're on the ABC7 News app, click here to watch live