SOUTH PLAINFIELD - A Middlesex County man and his mother face murder charges in the beating death of a South Plainfield volunteer firefighter.

The Middlesex County Prosecutor's Office announced yesterday the arrests of 37-year-old James Thomas and 53-year-old Shelley Thomas, both of Plainfield.

The two are charged in the death of 53-year-old William Koonz Jr., who was found dead Friday in his South Plainfield home after concerned relatives asked police to go there and check on him.

An autopsy determined Koonz died from blunt trauma to the head.

Prosecutors say the attack was not a random incident, but declined to provide further details.