One of two men accused of murder in connection with the vicious fatal beating of a homeless man in a vacant building near the Hawai‘i Convention Center last summer pleaded guilty in state court Tuesday to assault and has agreed to testify against his fellow defendant.

An Oahu grand jury returned an indictment in September charging Chu Lun K. Aiona and Nicholas Payne with murder for the Aug. 28 death of Joey Nguyen.

Aiona, 39, pleaded guilty in state court to the reduced charge of first-degree assault in a deal with the prosecutor.

He agreed to accept the maximum 10-year prison term for first-degree assault at sentencing in August and to serve at least one year of the sentence behind bars. The Hawaii Paroling Authority can set a higher minimum.

If he had been found guilty as charged, Aiona would have faced a mandatory life prison term with the opportunity for parole for murder, extended to life with no parole because he has at least two prior felony convictions.

Aiona has felony convictions on Maui and the Big Island for drug possession, auto thefts and break-ins and criminal property damage.

Deputy Prosecutor Kelsi Guerra told Circuit Judge Todd Eddins that Aiona’s plea deal includes a cooperation agreement.

Payne, 36, is scheduled to stand trial on the murder charge in June. He and Aiona remain in custody on $1 million bail.

The Honolulu Medical Examiner says Nguyen, 49, died from blunt force head injury.

A witness reported seeing Aiona and Payne block Nguyen’s attempts to escape, and kick and punch his face and body for 35-40 minutes on the second floor of the building at 1687 Kapiolani Blvd. The witness said Aiona accused Nguyen of a sexual assault and that Payne claimed to have been molested as a child.

Other witnesses told police that when they showed up, Nguyen was on the floor, barely alive, Aiona was no longer in the building and Payne, who was covered in blood, wasn’t telling them what happened. They said they got Payne to help them carry Nguyen out of the building to the bus stop fronting the building.

As they were trying to flag down police, the witnesses said, they turned around and saw Payne choking Nguyen. They said Payne fled after they stopped him.

Police said when the first officer arrived, Nguyen was bleeding from his face and head and had no pulse. A city ambulance crew arrived and tried to revive Nguyen. Nguyen was taken to Straub Medical Center where a doctor pronounced him dead.