The deputies are the only law-enforcement officers who discharged their weapons during the incident, which left seven people dead, including Rodger, and injured 13 others, according to Sheriff Bill Brown.
"We turned it over to department investigators to make a determination of whether they were lawful shootings," Brown told Noozhawk.
He said the results of that probe, which is expected to take several weeks to complete, will be turned over to the county District Attorney's Office for a decision on whether the shootings were legally justified.
The four deputies, whose names have not been released, were placed on administrative leave, which is routine procedure in these situations, according Sgt. Mark Williams.
Brown previously has said that at least one bullet struck Rodger in the hip while he was driving his black BMW 328i through the streets of Isla Vista, shooting at some people and running others down.
Although autopsy results were pending, Rodger is believe to have died of a self-inflicted gunshot wound to the head, Brown has said.
The first officer-involved shooting Friday night occurred as Rodger drove west on Del Playa Drive, Brown said.
A deputy responding to the area on foot was shot at by Rodger, who was armed with three semi-automatic handguns, and the deputy returned fire, Brown said.
In the 6600 block of Del Playa, Rodger struck and injured a bicyclist with his car before continuing to Camino del Sur, where he fired multiple times at pedestrians, three of whom were hit.
On Sabado Tarde Road, Brown said, Rodger shot another victim before coming into contact with four deputies running across the grass at Acorn Park.
Rodger fired at the deputies, and three of them were able to return fire, striking his vehicle and hitting him in his left hip.
Rodger then drove back to Del Playa, where he accelerated to a high rate of speed and struck another bicyclist, Brown said. The BMW then collided with several parked cars and came to a stop.
“Responding deputies removed the suspect from the car, handcuffed him and he was obviously dead with an apparent gunshot wound to the head,” Brown said. “It would appear as though he took his own life.”
District Attorney Joyce Dudley said that once the sheriff's administrative report is received, her office will conduct its own investigation, which will be reviewed and discussed by her senior staff.
Ultimately, the determination of whether the shootings were legally justified will be up to Dudley.
Brown said he could not provide additional details on the shootings, such as the number of rounds each deputy fired.
He also noted that there is an ongoing criminal investigation of the entire incident.
"We still do as thorough an investigation as if we were recommending that someone be prosecuted, even though in this case that person is deceased," Brown said, adding that the probe could take several months.