The ex-soldier, who reportedly cannot be named due to security reasons, was having coffee at the Westgate Mall in Nairobi when armed Islamic militants attacked on Saturday.
Witnesses said he went into action, returning to the building a dozen times and leading about 100 people to safety, according to the U.K.’s The Independent.
The former marine’s actions were revealed after he was photographed leading two women with what appeared to be a gun tucked into his pants, according to the Daily Mail.
“What he did was so heroic … he went back in 12 times and saved 100 people,” a friend of the man told The Independent. “Imagine going back in when you knew what was going on inside.”
The Independent reported that the man lives in Kenya full-time, a common practice for former Royal Marines after their service in east Africa.
More than 60 people have been confirmed killed by members of the Al Qaeda-linked Somali terrorist group al-Shabab.