A Mallinckrodt Center Subway employee says a four-minute-late order and payment dispute led to a customer throwing his unopened beverage at her shoulder.

The Washington University Police Department is continuing to investigate the alleged altercation between a campus employee and Subway cashier over an order.

Marlissa Vinson, 18, said she was working the cash register Thursday night when a University College staff member, already furious that his online order was not ready on time, got aggressive when she told him he had underpaid for his sandwiches.

Vinson said the customer had ordered a kid’s meal and two six-inch subs for a 7 p.m. pickup. He initially tried to pay for the kid’s meal and a footlong, and when she told him that he owed more money, Vinson said he proceeded to slam down his food order and throw his milk at her shoulder—though WUPD Chief of Police Don Strom could not confirm that any assault took place.

“It didn’t hurt then, but when I woke up the next morning, I had sharp pain [in my shoulder],” Vinson said. “And I’m like, ‘Did that really happen from that milk?’”

She said that the customer then demanded to see a manager—who offered to give him his meal for free—but the customer refused and began verbally accosting the manager as well.

Strom said that WUPD was called around 7:15 p.m. and officers arrived shortly after. But by that point, Vinson said the manager had demanded that the customer exit. Strom said no one was hurt and the customer had left by the time police responded.

The investigation is ongoing, but WUPD has reached out to the man it believes is responsible. Strom said they will handle the process internally and decide whether to refer the case to a county prosecutor.

“This is my first job, so it’s crazy,” Vinson said.

The man Vinson claimed was responsible did not return a Student Life request for comment Sunday evening.