Los Angeles (CNN) -- Six Fullerton, California, police officers were placed on involuntary administrative leave as the FBI and Orange County District Attorney investigate the death of a homeless man who was in police custody, authorities said Wednesday.

The decision by Police Chief Michael Sellers came just hours before a contentious Fullerton City Council meeting Tuesday evening. More than 100 residents spent three hours at the meeting expressing outrage about the death of Kelly Thomas, who sustained serious injuries during the July 5 arrest by the officers, a police spokesman said.

"They're pretty much homebound," police spokesman Sgt. Andrew Goodrich told CNN Wednesday. The officers will remain on salary; their names weren't released, he said.

"Any sort of termination, suspension or exoneration for the matter will occur at the end of the investigation," Goodrich said.

During Tuesday evening's council meeting, Thomas' father, Ron, expressed anger about how his son died in police custody. He accused the police of beating his son.

"I just wonder where my son's rights went as a citizen," Thomas told the council. "Where were his rights? Listen to my son beg those officers, 'Please, please, God, I'm sorry, I'm sorry.' And the last words of his life, 'Dad! Dad!' I want you to hear that for the rest of your life like I will."

The FBI is investigating whether Kelly Thomas' civil rights were violated during the incident, said Laura Eimiller, spokeswoman for the FBI's Los Angeles office.

The Fullerton police have classified the incident as an "in-custody death," Goodrich said.

The incident between Kelly Thomas and the police officers, at a Fullerton bus depot, was captured on video, local authorities said.

"There are things that you can see and there's things you can't," Susan Kang Schroeder, chief of staff for the Orange County District Attorney's office, told CNN about the video. "Your heart is sad watching what happens in the case."

So far, the district attorney's office has interviewed 80 persons, and it is expected to interview 20 more, Schroeder said.

Authorities haven't established an official cause of death and are awaiting results from a coroner's autopsy and toxicology tests, Schroeder said.

On July 5 at around 8:30 p.m., officers responded to reports that a man was trying to break into cars near the city bus depot three blocks from city hall, police said. Fullerton is 30 miles southeast of downtown Los Angeles.

The responding officers identified the suspect as Kelly Thomas, 37, a homeless man who frequented the area, police said.

An altercation took place between the police officers and Thomas. Thomas sustained serious injuries during his arrest and was taken to a local hospital, police said. Five days later, Thomas was removed from life support and died, police said.

Upon the police department's request, the Orange County District Attorney took over the investigation of the case, police said.