It all unfolded at Honolulu Jewelers on the 2200 block of Honolulu Avenue.
Authorities said the suspect was pretending to deliver a package Saturday morning.
When a store employee approached him to sign for it, the suspect pulled out a gun and pistol-whipped him.
The robbery has owners of nearby businesses questioning if there's anyone they can trust nowadays.
"It's pretty scary. Now it makes us try to rethink everything now. Great, one more thing to worry about," said nearby business owner Tony Camarelli.
Police said the suspect got away with an undisclosed amount of jewelry.
The store employee suffered minor injuries to his face but was expected to be OK.
If you have any information that could help investigators catch the suspect, call Glendale police at (818) 548-4911.