Los Angeles (CNN) -- A police officer in Fullerton, California, whom an attorney accuses of brutality in the death of a homeless man this summer and two arrest cases last year, has been placed on paid leave, a police spokesman announced Friday.

Sgt. Andrew Goodrich identified the officer as Kenton Hampton, but he declined to confirm whether Hampton is among six officers involved in the arrest of Kelly Thomas, a 37-year-old homeless man who died five days after allegedly being beaten by police this summer. That death is under investigation by the FBI and the Orange County District Attorney.

But Hampton was involved in two incidents last year in which two men are accusing Hampton of brutality and false arrest, Goodrich told CNN.

"I can't comment as to the type of leave or the reason or the length," Goodrich said of Hampton being placed on paid leave. In making the announcement Friday, Goodrich declined to state when the leave became effective.

Hampton and his attorney couldn't immediately be reached for comment Friday.

Goodrich confirmed that Hampton was the officer involved in a new allegation of brutality made Friday by Edward Miguel Quinonez, 27, of Anaheim, California, who is planning to file a lawsuit against Hampton for "slamming" his head against a wall in a June 27, 2010, incident. His attorney, Garo Mardirossian, who's also the lawyer in the two other alleged brutality cases, announced the plans in a press conference Friday.

Fullerton police investigated a police misconduct complaint filed by Quinonez shortly after the arrest, Goodrich said.

"That complaint was investigated, and there was a disposition on the complaint, and I can't talk about the disposition," Goodrich said.

Quinonez's case marked the third case of alleged brutality by the Fullerton police. Those three accusations emerged this summer in the wake of the death of Thomas, a homeless man who was diagnosed as a schizophrenic.

Quinonez accused Hampton of assaulting him and falsely accusing him of being drunk in public, said Mardirossian.

Coincidentally, Quinonez happened to be one of about 100 witnesses to the police struggle with Thomas and even saw Hampton's involvement in that incident, Quinonez said. Quinonez was interviewed by prosecutors investigating the homeless man's death, his attorney said.

In the 2010 incident, the officer was writing a ticket to a motorist for bouncing his lowrider and displaying its hydraulics as Quinonez happened to be on the sidewalk, waiting outside a bar, Quinonez told reporters Friday.

The officer told Quinonez not to interfere with the investigation, and Quinonez then responded: "Get away from me because cops killed my dad," who was shot to death by Riverside, California, police on September 1, 2008, Quinonez said.

That remark was apparently interpreted by the officer as "contempt of cops," Mardirossian said.

The Fullerton officer then arrested Quinonez and slammed his head against the wall, Quinonez said.

A blood test later showed that Quinonez had no alcohol in his system at the time of the arrest, he and his attorney said.

Quinonez filed a police misconduct complaint just days after the incident, but he said he didn't know if anything ever became of the complaint, though he made several follow-up phone calls.

"As it says on the side of the patrol car, they are there to serve and protect us, not harass us," Quinonez said. "He acted out of the heat of passion by throwing that charge at me, which was very unethical for him to have done, to take his personal issues out on me.

"He threw handcuffs on me and he slammed my head up against the wall, and he applied pressure to my head, which made my head hurt worse," Quinonez said. The officer spoke in "like a sarcastic tone when I asked him what I was going to jail for, and he laughed and said, 'drunk in public.' He had to think about it."

The other two instances of alleged police brutality occurred after Quinonez's complaint, he said.

"If they would have taken care of the matter when I filed the complaint, then this wouldn't have happened," Quinonez told reporters, referring to the two other alleged instances of brutality.

During the press conference, Quinonez was seated next to another alleged victim of police misconduct, Veth Mam, who is suing the Fullerton police for an incident that occurred four months after Quinonez's experience.

Added Mam: "If (Fullerton police) would have taken action on (Quinonez's) behalf, I probably wouldn't be in this mess, and Mr. Kelly Thomas wouldn't have passed away."

Mardirossian, who's the attorney representing the alleged victims in all three instances, said the cases show "a pattern" of police misconduct. "We need to identify rogue cops and get them off the street. These few bad apples give the entire department a bad name," he said.

In the Thomas incident on July 5, Quinonez happened to witness police "beating on Kelly Thomas" as Quinonez was boarding his bicycle on a bus near the altercation, he said.

Quinonez said he heard Thomas crying for his father, Ron, who also was at Friday's press conference.

As he witnessed the encounter between police and Kelly Thomas, Quinonez saw the same officer from his arrest "walking up, and that's when the whole beating process started" in the Thomas arrest, Quinonez said.

The officer was also allegedly involved in a third case of suspected police brutality last year in which Mam, 31, of Baldwin Park, California, has filed a civil lawsuit against Fullerton police, said Mardirossian.

Mam's altercation with Fullerton police officers was recorded on his iPhone and posted on YouTube. Mam wasn't seriously injured, Mardirossian said.

During the early morning hours of October 23, 2010, Mam was recording the arrest of a friend on his iPhone camera.

Instead of documenting what Mam described as a case of excessive force, the 31-year-old factory worker was himself arrested and charged with assaulting a Fullerton police officer.

Last month, Mam filed a civil lawsuit, claiming that Hampton and other officers falsely arrested him, conspired to violate his civil rights and committed perjury during his misdemeanor trial. Mam, who lives with his girlfriend in nearby El Monte, was acquitted of battery against an officer and resisting arrest last month.

On Friday, police spokesman Goodrich confirmed that Hampton was one of the officers involved in Mam's arrest.

Fullerton acting Police Chief Kevin Hamilton has launched an internal affairs investigation into the incident, and police have said there is "a strong possibility" they wrongly arrested Mam, a spokesman said.

In the Thomas case, medical records made public this month by Madirossian show that Thomas died from brain injuries as a result of head trauma.

The records were compiled by physicians at the University of California Irvine Medical Center while Thomas remained on life support after the violent struggle.

"By the time he got to the hospital he was already brain dead," Mardirossian said earlier this month.

Thomas was a diagnosed schizophrenic who was homeless at the time of the altercation, his attorney said.

The medical records showed that Thomas suffered blunt head trauma with multiple broken bones in his face, and with rib fractures, according to Mardirossian. Thomas died five days after what the Orange County district attorney has called "a violent and desperate struggle" with Fullerton police.

Thomas was shocked multiple times near his chest cavity and on his back with a Taser stun gun, said Mardirossian.

According to the medical records, Thomas also suffered nose and brain trauma, and smashed cheekbones.

Mardirossian claimed that officers used their Taser guns to deliver some of the head and face blows.

The examination also concluded that Thomas had no narcotics or prescription medications in his body, Mardirossian said.

Several bystanders witnessed the encounter and others recorded portions of the beating on cellular phones, according to Mardirossian.

According to the medical report, Thomas suffered severe internal bleeding. "The medical evidence will show that all that blood is what he ended up choking on," the attorney said.

Thomas' father, Ron, who once worked briefly as a law officer, has filed a claim against the city of Fullerton.

The Orange County Coroner's office has not determined the official cause of death, pending toxicological findings, officials said. The Fullerton police department has declined to comment about the medical reports.

Since the Thomas incident, six officers allegedly involved have been placed on involuntary paid administrative leave. City officials have not released their names.

Police Chief Michael Sellers has taken a paid medical leave, and two of the city's five council members have called upon him to resign.

Meanwhile, there are two external investigations into the death by the FBI and the Orange County district attorney's office. The FBI is looking at possible civil rights violations.

The Thomas incident began when police responded to reports that a man was trying to break into cars near a bus depot three blocks from City Hall.

Following the beating, there was no evidence that vehicles were burglarized nor was Thomas in possession of any stolen property, according to Mardirossian.

CNN's Stan Wilson contributed to this report.