CHICAGO (CBS) — When dining out, a 20 percent tip is usually considered standard.

However, the tip the staff got at Lincoln Park’s Boka restaurant on Sunday night was anything but typical.

Server Brandon Anderson says a customer named Mike dined with five friends before heading off to a concert.

Before leaving, Mike thanked Anderson for his service and meal and then asked to thank the kitchen staff.

Mike spoke with the 17 kitchen members and then gave them each a $100 bill.

“We were all speechless,” said Anderson.

Then, he left Anderson a $200 tip on his $400 dollar tab.

Staffers say they don’t know anything about Mike except he’s from Seattle and this was his first time in Chicago.

“He definitely came across as extremely genuine,” said sous chef Richard Graham. “It came from the heart. It didn’t seem like a stunt or some rich snob or anything like that.”