- The incident came to light after a customer posted photos on social media
- In a series of tweets, the grocery chain says it is investigating
(CNN)Whole Foods Market has fired a security guard who allegedly beat up a man trying to buy groceries this week in Northern California.
The incident came to light after customer Zoe Marks posted photos on social media showing a man bleeding on the ground.
She said she took the photos at a Whole Foods in Oakland. It's unclear why the man was allegedly attacked.
"I just saw a young man violently assaulted by an armed security guard at Whole Foods -- slammed repeatedly against concrete pillars, put in a chokehold, restrained and suffocated until he was thrown face down on the pavement unconscious," Marks said in the post.
"The guard locked him out of the store despite the fact he was immobile."
Marks tweeted multiple times including directly at Whole Foods Market, asking it to get to the bottom of the incident, and the company answered her.
"@z_marks We take this very seriously. We are investigating this immediately," Whole Foods tweeted back.
Whole Foods spokeswoman Beth Krauss told The San Francisco Chronicle that the guard "interceded when the customer made physical contact with a team member inside the store."
In a series of tweets Friday, the grocery chain said it is investigating the incident.
"We're moving quickly to gather the facts, we want to make it clear that we take a zero tolerance approach to violence," it said. "The security guard involved in the incident has been permanently removed from all WFM stores."
Oakland police spokeswoman Johnna Watson told CNN affiliate KGO that they received a call Thursday night about an unconscious man at the store.
The man is in stable condition, the affiliate said.
Authorities did not identify the security guard or the man attacked.