A black-clad gunman ambushed two undercover detectives returning to a police station early Tuesday, but their wounds didn't prevent them from aiding the hunt for the attacker.
Police Chief Charlie Beck described the shooting as an attempted assassination and mobilized a huge search involving helicopters, dogs and about 200 officers.
Police initially cordoned off 25 square blocks of the Mid-City area of Los Angeles, leaving thousands of residents stranded in homes and forcing drivers to find detours for their morning commutes.
Later in the day, the search focused on a neighborhood just south of the LAPD's Wilshire substation, where the attack occurred.
At least 10 people were detained for questioning and released. Police also planned to look at surveillance video from homes and businesses.
"Anybody who's willing to do this and take on two armed police officers outside of a police station is obviously a very dangerous person," police Cmdr. Andrew Smith said.
The detectives who were attacked are assigned to an undercover burglary task force and were returning to the station about 4:30 a.m. They were using a keycard to open a gate as shots were fired, police said.
"Suddenly someone from behind began shooting at their vehicle," Smith said.
The car was hit several times and the detectives fired back as the man ran away, Smith said. The gunman and detectives fired more than a dozen shots, he said.
One officer suffered a minor wound to the back of his head, either from a bullet graze or debris from the damaged car, Smith said. The other had an injury to the back of his hand. Their names were not released.
They were treated at a hospital and returned to a command post for the manhunt. One detective has 20 years on the job and the other is an 11-year veteran, Smith said.
The shooting was believed to be an isolated attack, but as a precaution all other police stations were notified to be on high alert, Smith said.
AP writer Tami Abdollah contributed to this report.