The Honolulu Police Department has opened a manslaughter investigation involving two officers after a 77-year-old man died from injuries suffered during a late-December arrest for an alleged moped theft.

HPD Chief Arthur “Joe” Logan announced the investigation Wednesday at a news conference at HPD’s Beretania Street headquarters.

On Dec. 28, two District 1 Crime Reduction Unit officers stopped the man, identified as Thomas Matias of Honolulu, who they believed was operating a moped identified as stolen in HPD’s database, in the Ala Moana Center parking lot, said Logan. The chief stressed that the information was based on a preliminary investigation.

The officers used force to make an arrest, which resulted in Matias “sustaining injuries to his face and torso,” he said.

Matias was taken to the hospital after the arrest, but reportedly refused treatment. He was booked for unauthorized control of a propelled vehicle and released, according to Logan.

Two days later, paramedics and police officers went to Matias’ apartment to provide medical assistance, where he told officers that “he had been assaulted by police officers two days earlier,” the chief said.

Matias was taken to the hospital again, where he was found to have multiple fractures of his ribs and face. He left the hospital several hours later “for reasons unknown at this time,” Logan said.

Matias was found dead at his home on Jan. 10. Shortly after his death, the CRU officers, who were not identified, were placed on restricted duty. They have three years and eight years of service respectively, according to Logan.

A statement from the Honolulu Medical Examiner’s office says Matias’ cause of death was “combined effects of atherosclerotic coronary artery disease and acute bronchopneumonia, recent rib fractures, blunt force trauma of the chest and pulmonary emphysema.” The manner of death was homicide.

Logan said that the medical examiner’s office defines homicide as a “volitional,” or deliberate, act that causes harm that results in or contributes to a person’s death. Homicide does not indicate or imply criminal nature of the act, criminal intent or wrongdoing, he said.

A first-degree assault investigation was opened on Jan. 16, but following autopsy results from the Honolulu Medical Examiner’s office, the case was reclassified Wednesday to manslaughter.

“With the cause (being) combined effects of existing medical conditions and recent chest and hip injuries, the case will be reclassified to manslaughter,” Logan said.

At the time of the incident, HPD was conducting “hot spot” policing operations in the Ala Moana area — an area that is known for vehicle crime, Logan said. The CRU officers conducting the hot spot policing operations were plain clothes officers.

There is no body-worn footage from the incident, as plain clothes officers are not given body cameras. Some surveillance video footage is available, and is being used as part of the investigation.

When asked if the man was resisting arrest, Logan said that the investigation “will play that out.”

“I think we need to know more information as to the engagement between the use of force and why,” he said.

The manslaughter investigation is being conducted by HPD’s Criminal Investigation Division and the Professional Standards Office.

The standards office is also conducting “an administrative investigation for violations of department policies and procedures,” which will also include reviewing the actions of the officers who responded to the man’s home after his initial arrest, Logan said.

The officers involved in the incident have not been charged, and the investigations are ongoing. Logan said that it will probably be “several more months” before the investigation is concluded, at which time the case will be taken to the Department of the Prosecuting Attorney.