Sheriff's deputies say two adults and one juvenile had stolen two cases of beer from Dooly's Liquor & Market on 14th and Walnut streets at about 10 p.m. Sunday.
The suspects got away, and deputies came and took a report on the misdemeanor theft. But then they returned to the business to get the surveillance tape, authorities said.
The suspects, ages 17, 18, and 19, threatened the store owner with a knife and cut his arm.
"They said, 'Give us the tapes,' because they knew they were on tape from the first time. But coming back for them the second time is not a good idea," said clerk Daniel Ramirez.
When the clerks did not provide the video, the suspects got violent.
"We walked out the door, and they had some of their friends waiting out here for them, and as soon as we came out, one of them was holding a beer bottle and just broke it on the ground and came at us, and we just had to defend ourselves," Ramirez said.
Police were able to arrest one of the suspects as he left the store. The other two suspects were arrested shortly after.
Not only did the suspects make it easier for authorities to find them by returning to the scene, but they intensified the charges against them, going from what would have been a misdemeanor to a felony.
"It would have been a petty theft, a beer run ... to assault with a deadly weapon," said Lt. Stephen Low of the Los Angeles County Sheriff's Department.
The investigation is ongoing. Police said after reviewing the surveillance tape, there may be more suspects.