The alleged attack late Sunday by Jessica Hill, 21, and Jayla Hill, 18, left the 32-year-old victim hospitalized in critical condition, police spokeswoman Karie James said.
An argument that began after the women refused the guard's request to wear masks became physical when one of the women punched the man, James said. Jessica Hill allegedly pulled a knife from her back pocket and began stabbing the man, while Jayla Hill held him in place by his hair. The man was stabbed in his chest, back and arms.
The women were arrested at the scene of the attack and both were treated for minor lacerations at a nearby hospital, James said.
During Tuesday's bond hearing before Cook County Circuit Judge Mary C. Marubio, the women's court-appointed attorney said the stabbing was self-defense, adding both women suffered from a bipolar disorder.
Prosecutors said the guard never approached either women before the attack.