It was all caught on camera at about 4 p.m. Thursday at the Cigar and Smoke Shop at the intersection of Artesia and Aviation boulevards.
In the footage, the man is seen walking into the store with a long cardboard box. He strikes up a conversation with the clerk, then suddenly pulls out a shotgun from that box, points it at the clerk and ushers him to the back of the store.
Authorities say the suspect handcuffed the worker then returned to the front of the store and took all the money from the cash register. Police said that's when the suspect returned to the back of the store, took out a knife and slit the worker's throat.
According to investigators, that worker was able to dial 911 after the attack. He was rushed to the hospital for emergency surgery. He was reported in stable condition and expected to recover.
The suspect is described as a black man in his 30s with a thin build, a light mustache and short hair. If caught, he will be charged with robbery and attempted murder.
If you have any information about this case, you're urged to call Manhattan Beach Police at (310) 802-5140.