CHICAGO (CBS) – Armed robbers left something behind at a Ukrainian Village pizzeria: clear images on surveillance video for police to analyze.

Police say the stickup occurred a little after 5 a.m. Friday.

Newly installed cameras at John’s Village Pizza on Chicago Avenue captured the crime.

Two men entered the restaurant and ordered slices. Suddenly, they came around the counter and one of the men pointed a gun at the owner, John Gagliardi Sr., and then demanded he get cash from the register.

The armed man then punched Gagliardi in the face. The second man hit him in the back of the head.

“For two gentlemen to come in here and hit him and put guns in his face is not right,” the owner’s son, John Gagliardi Jr., told CBS 2’s Mike Parker on Friday night.

The owner and a female employee, Diana Cregan, tried to open the register. Finally, the owner was able to open it, and the two robbers grabbed $300 in cash and made their getaway.

But in their haste, they dropped some of the loot.

“We were a nervous wreck,” Cregan said. “I guess I’m going to be watching everybody that walks through this door.”

Police have no suspects in custody.

“My dad is a good-hearted guy,” Gagliardi Jr. said. “Anybody who comes in here who doesn’t have money, he gives out slices to people. He treats people with respect, and there’s no more respect today.”