LAWRENCEVILLE — A Gwinnett County Sheriff’s Department deputy is expected to recover following a violent attack by a jail inmate whose mental health has recently been questioned, according to officials and court documents.

Deputy William Lamb, 47, was working a housing unit Wednesday evening when inmate James Leon Washington, 18, suddenly attacked, striking the deputy in the face and pounding his head into a concrete floor, said Sheriff’s Department spokeswoman Stacey Bourbonnais.

Two other inmates rushed to Lamb’s aid, pulling Washington away and restraining him until other staff members could respond, Bourbonnais said.

Lamb was unconscious and unresponsive when deputies first arrived. He was transported to Gwinnett Medical Center, where he was treated and released Wednesday night, Bourbonnais said.

Lamb, hired at the department in 2006, is expected to fully recover, she said.

Questions linger as to what allegedly set Washington off, but court documents provide glimpses into his apparent bloodlust. Family members warned prosecutors in a recent letter that Washington is mentally unstable and an extreme societal threat.

“The attack was sudden and without warning, and no motive has been determined,” Bourbonnais said.

Washington has been jailed since May on charges of criminal damage to property, second-degree, and violation of probation. Additional charges are pending, Bourbonnais said.

Records show the arrest was Washington’s fourth in a year.

Washington was transferred to a cell in J-Pod, a maximum security area of the detention center for inmates with disciplinary problems.

Inmate-deputy clashes are rare. The incident marks the first serious altercation involving an inmate and deputy since 2003, when a 25-year-old obstruction suspect bit off a portion of a sergeant’s ear during an outburst and subsequent struggle, Bourbonnais said.

“Other than those two incidents, there have been no other serious attacks on staff members that I’m aware of,” she said.

Washington’s recent legal troubles began Aug. 27 last year at Hooper Renwick School in Lawrenceville, a school for special-needs students.

School resources officers arrested Washington on disruption charges when he began screaming during a lunch hour, causing a cafeteria’s evacuation, according to a Gwinnett Public Schools police report.

The next month, Washington was arrested by Snellville police on felony aggravated assault charges for chasing someone with a knife. He exercised the First Offender Act and was sentenced to six months jail time and six years probation.

Upon Washington’s April release, Superior Court Judge Warren Davis ordered him to complete an anger management program and mental health counseling with psychotropic medication as prescribed.

On May 10, Gwinnett police arrested Washington for an alleged rampage at a Cruse Road home. He smashed the home’s windows and a car’s windshield with furniture, then the furniture with his foot, thereby violating his probation, according to an arrest warrant.

Weeks later, Washington penned an ominous jail letter to his legal guardians, Gina and Barry Washington, in which he threatened to kill them and wished “a painful death” on other family members.

“I will put a price on you’ll (sic) death or kill you’ll myself,” Washington wrote, according to documents in his case file.

In response, Gina Washington wrote to Davis, the judge, and a mental health facility that Washington is “clearly a threat to me and my husband and the rest of my family,” another letter says. “My suggestion is that he not be released into any community. He clearly has a mental illness that is soaring out of control.”

By Thursday afternoon, Bourbonnais said Lamb, the injured deputy, was recuperating at home.

She credits the inmates who intervened — Daniel Allen, of Alpharetta, and Kenneth Robinson Jr., of Jasper — with preventing a bad situation from getting worse.

Allen has been jailed since December on robbery, battery and assault charges, and Robinson since June for allegedly violating his probation.

“Had the inmates not intervened, it could have been much worse,” Bourbonnais said.