It was unclear whether anyone was struck by the pre-dawn gunfire, said LAPD Officer Matthew Ludwig.
The first shooting was reported shortly before 1 a.m. at 11th Place and Union Avenue, Ludwig said. Officers assigned to the LAPD's Rampart Division responded to the area and found shell casings, he said.
While at the scene, the officers "observed and heard another shooting," Ludwig said. One officer then spotted a suspect, who pointed a gun at the officer, prompting the officer to fire, Ludwig said.
Ludwig said police had detained three possible suspects, none of whom had been struck by gunfire. No victims had come forward by mid-Monday morning, he said.
The officer fired at the suspect near Olympic Boulevard and Albany Street, just a few blocks away from where the first shooting was reported. Ludwig said investigators were looking at "a few different crime scenes."