Sebastian M. Pietrzyk, 25, of Lake in the Hills, and Nikolis D. Thurnau, 33, of Marengo.

Two inmates were charged with beating a fellow inmate during an attack at the McHenry County Jail earlier this month, court documents allege.

Nikolis D. Thurnau, 33, and Sebastian M. Pietrzyk, 25, are both charged with aggravated battery causing great bodily harm, aggravated battery and mob action, which are all felonies.

Pietrzyk and Thurnau are accused of causing great bodily harm to a 30-year-old man, who was also being held in the McHenry County Jail, during a January 9 incident, according to a criminal complaint.

Pietrzyk and Thurnau allegedly struck the man several times with their fists and knees inside Block 2 of the jail, the complaint said.

Thurnau, of the 500 block of Grace Street in Marengo, has been held in the McHenry County Jail since July on charges of aggravated battery to a peace officer, aggravated assault on a peace officer and two counts of domestic battery.

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In that case, Thurnau caused bodily harm to a woman, who is a family member, by pushing her to the ground, court documents said.

Thurnau then allegedly hit the woman in her pelvic area, injuring her, after he pushed her to the ground.

Thurnau punched a responding police sergeant and attempted to bite him, court documents said.

Pietrzyk, of the 600 block of Anderson Drive in Lake in the Hills, has been held in the McHenry County Jail since late October after violating probation in a domestic battery and threatening a public official case.

Thurnau, who remains held on a $100,00 bond, is scheduled to appear in court again on Wednesday to schedule a preliminary hearing date.

Pietrzyk, who remains held on a $75,000 bond, is scheduled to appear in court again on February 4 for a preliminary hearing.