The incident took place near Wilshire Boulevard and Grand Avenue around 10 p.m.
The victim, identified as a man in his mid-40s, was pronounced dead at the scene.
Witnesses directed police to the suspect, a man in his mid-20s, who was then arrested.
The investigation is ongoing. Detectives were checking surveillance videos from nearby buildings to see if anyone else was involved.
"We're not 100 percent sure yet," about whether there could be a second or third suspect," said Sgt. Janet Kim of LAPD's Central Station. "We're looking at surveillance videos."