"Once again our hearts are broken," Los Angeles Police Protective League President Tyler Izen said in a statement. "This is a hard time for the LAPD family."
The latest death occurred Saturday morning.
Two officers were making a U-turn to follow a car moving at high speed when they were broadsided by an SUV about 3:55 a.m. near the intersection of Senator Avenue and Anaheim Street, said LAPD Cmdr. Andrew Smith.
The officer killed in the collision, 32-year-old Roberto Sanchez, was a six-year veteran assigned to the Harbor area, police said. His partner was in critical but stable condition at Harbor-UCLA Medical Center on Saturday. He is expected to survive.
Sanchez was the third LAPD officer killed this year. In March, an officer was killed in a crash involving a truck in Beverly Hills. In April, an LAPD motorcycle officer died after being hit by a suspected impaired driver.
Los Angeles police investigators are still trying to determine the circumstances leading up to Saturday's collision.
Speaking at a morning news conference, LAPD Chief Charlie Beck said that many important questions remained unanswered. "Only two individuals know exactly what the officers were doing," he said. "One is severely injured. The other one is deceased."
By midmorning, Smith said investigators had been able to string together only a "really, really preliminary" idea of what occurred.
Based on the positions of the vehicles and the account of the severely injured officer, he said, it is believed that the patrol car at the time was following a white Camaro traveling east on Anaheim Street.
The Camaro and the patrol car both made U-turns. The third vehicle involved in the accident, a Chevy Tahoe, also heading east, plowed into the driver's side of the patrol car as the officers were completing their turn, Smith said.
He said the department did not yet know whether the patrol car's sirens or lights were on at the time, or whether drugs or alcohol may have been a factor in the crash.
The driver of the SUV who hit the patrol car fled the scene on foot. The crash was so severe that the patrol car radio was inoperable and the surviving officer had to use his cellphone to call for help, Smith said.
Police located and detained a "person of interest" about a mile from the accident, he said, but no arrests have been made in connection with the crash.
No other information was available about the individual, who may have been the driver or a passenger in the vehicle.
"We're trying to ascertain his involvement in the situation," Smith said, noting that because the cars involved were destroyed, investigators will have to look at video footage from the patrol car to figure out what happened.
"It's really tough," he said.