MIAMI — A Miami police officer was justified in handcuffing and detaining a black doctor outside his home last month, an internal investigation has found, though the review also determined that the officer had violated department rules by yelling at the doctor and not wearing a face mask.

The department found that the officer, Sgt. Mario Menegazzo, believed that Dr. Armen Henderson, who was picking up bags and boxes next to his white cargo van on April 10, was illegally dumping trash in his Miami neighborhood, according to an internal police memo dated May 4.

Dr. Henderson, 35, who was featured in a Miami Herald article about volunteers who provide free coronavirus testing for the homeless, has said he was loading his van with tents to take to homeless people in downtown Miami when the officer approached him.

On Monday, he said he was disappointed by the outcome of the investigation and planned to file a lawsuit against the department.

“I felt that it was ridiculous that, No. 1, that the stop was justified, and then the detainment was justified as well,” said Dr. Henderson, who practices internal medicine in the University of Miami Health System. “It’s like, when are we going to start holding people accountable for their actions? I was very sad, very disgusted at the report I read.”

The police memo noted that residents had filed more than a dozen complaints about illegal dumping in the neighborhood in the months before Sergeant Menegazzo’s encounter with Dr. Henderson, video footage of which was shared widely online.

“As a sworn police officer, Sergeant Menegazzo had the right to detain Dr. Henderson until his reasonable suspicion that Dr. Henderson was dumping illegally was dispelled,” the memo stated.

The internal affairs investigation found that Sergeant Menegazzo had violated other department policies by yelling and pointing in Dr. Henderson’s face; by failing to wear a face mask, as the Miami department is requiring of officers during the coronavirus pandemic; and by failing to notify dispatchers that he was conducting an investigative stop.

The memo did not say whether Sergeant Menegazzo would be disciplined. Chief Jorge Colina of the Miami Police Department said in an interview that the sergeant would be reprimanded on the violations and that they would become part of his file.

The investigation was ordered after Dr. Henderson filed a complaint with the Police Department’s Civilian Investigative Panel.

In a statement to the Police Department, Sergeant Menegazzo said that he had stopped Dr. Henderson because of “the numerous complaints of illegal dumping” in Flagami, Dr. Henderson’s neighborhood on Miami’s west side.

In an interview last month, Dr. Henderson said Sergeant Menegazzo “asked me if I lived there and if I was littering.” Dr. Henderson said he explained that the curb was where the city collected bulk trash each week.

He said the officer asked him for identification. Dr. Henderson said he replied that he did not have it on him and would have to retrieve it.

Dr. Henderson said he turned around to resume his work, and the officer handcuffed him.

Sergeant Menegazzo said in his memo that Dr. Henderson “appeared upset and agitated” as he tried to confirm that the doctor lived there.

Dr. Henderson was eventually released from the handcuffs after his wife, Leyla Hussein, who was inside their home with their two children, came outside and showed identification to the officer.

A day after the episode, Chief Colina ordered an internal investigation into the matter and said that his department “does not condone or accept profiling of any kind.” He said Monday that he was satisfied with the outcome of the investigation.

“If we make a mistake, we need to own that mistake, correct it and move forward,” he said. “But it should be factual.”

Dr. Henderson said last month that he was upset that the officer was not wearing a face mask during the encounter, which he described as an incident of racial profiling.

“Sergeant Menegazzo stated that he did not stop Dr. Henderson because he was black,” according to the investigative memo, and that “if Dr. Henderson had been white or Hispanic, he would have acted in the same manner.” The memo said that Sergeant Menegazzo had not been previously accused of racial profiling.

But Dr. Henderson said he would pursue a lawsuit because he believed he had been racially profiled. He also said he believed “the officer put my life in danger by not having a mask on.”