Surveillance video shows the crime in progress, and Tuesday night, police are looking for the band of thieves.
The robbery happened in west suburban Cicero at the Roosevelt Gold Exchange.
The suspects appeared to be in their teens or 20s, and after breaking into the Roosevelt Gold Exchange, they terrorized the clerk.
"He thought his last moments were yesterday at about 1:30. He had a pillow case put on his head and thought he was going to be killed," said Louie Rainone, owner of Roosevelt Gold Exchange.
Rainone wasn't there at the time. His 41-year-old clerk was alone, but Rainone saw it all on a surveillance video.
"I work hard for a living, and to see punks come and trample all over what I try to build for my daughter, I mean it's terrible," said Rainone.
Police say as many as five men may have been involved after arriving in a white minivan with left front-side damage.
While three of the suspects pretended to sell the clerk a silver chain through the security glass, one man pried the door open with a crowbar.
Once inside, the suspects covered the clerk's head with a pillow case, wrapped a phone cord around his neck, and beat him.
"They have a crowbar in their hand, and they're telling him they're going to kill him. It's terrible," said Cicero Town Spokesperson Ray Hanania.
After ransacking the room and stealing jewelry from this unlocked safe, the suspects tried to take the surveillance disc in the other room, but were confronted by Fatty the bulldog and his pal Max, a110-pound French mastiff.
"Where's the bad guys?" said Rainone with his dog. "They didn't get that tape, did they?" he said, the dog barking. "They didn't get that tape!"
In all, the thieves stole $40,000 worth of jewelry.
But they left one curious item, a Mike Ditka Bears rookie card, valued at a few hundred dollars.
"We got your picture, guys. Good work. Save that money for commissary. You're gonna need it," said Rainone.
Investigators are asking for the public's help in locating the culprits.