EVERETT — One of three suspects facing murder charges in the December death of an Everett man has pleaded guilty to a different crime.

Patrick Rex Griffiths, 35, pleaded guilty to first-degree robbery with a deadly weapon.

The murder charge was dropped as part of a plea agreement that requires him to testify at the trial of co-defendants defendants Jimmy Ruiz, 44, and William Gobat, 34.

Prosecutors allege that the trio attacked Donald Barker, 37, outside Madison Elementary School. A neighbor found Barker lying in a grassy area. He told the man he’d been “jumped” by a few guys and he was hurt badly. Barker died on the way to the hospital.

The medical examiner found numerous injuries, including two deep stab wounds to the chest and back. He also suffered a serious blow to the head, court papers said.

In his plea agreement, Griffiths said one of the other men was armed with a knife. He admitted stealing Barker’s cellphone.

Prosecutors are recommending a sentence of more than 16 years in prison.