A 29-year-old man already charged with two counts of first-degree murder also faces an additional felony charge related to a report of an attempted jail assault, according to court documents and the Lane County Sheriff’s Office.

Police in July arrested Justin Ray Carr in Washington state on suspicion of intentionally setting a fire July 9 at a Springfield mobile home park that killed two relatives.

Elizabeth Rae Boggs, Carr’s 85-year-old grandmother, sustained injuries in the fire and later died. Her son, Michael Gary Boggs, 64, was found dead inside a home at the Santiago mobile home park.

On Aug. 14, Justin Ray Carr attempted to assault another person in custody at the Lane County Jail, said Sgt. Tim Wallace with the Lane County Sheriff’s Office. Carr is suspected of attempting to cause “significant injury,” Wallace said in an email.

Prosecutors have formally charged Carr with attempting to commit a Class B felony in connection with the alleged attempted jail assault. The charge carries a maximum penalty of five years in prison.

Carr’s next scheduled court appearance is Oct. 27, with a trial on the murder charges set for November of next year. Carr has also been charged with first-degree arson.