Investigators said 47-year-old Raymond Link approached a woman who was walking her dog on a leash at about 3:26 p.m. Sunday and attacked her, punching and kicking her in the head and neck.
Prosecutors said when she was on the ground, Link allegedly tried to strangle her. He also called on his dog, who was not on a leash, to attack her.
Another man in the area then tried to intervene and help the woman.
"I understand there was man who was a spectator out there who was able to jump in and help that lady, which is a remarkable thing. He should be given recognition for that," said Sean, a neighbor.
Police said the suspect then punched the Good Samaritan a number of times. His dog also allegedly bit him. That Good Samaritan suffered minor injuries.
The woman's injuries apparently more serious. She was flown by helicopter to Advocate Condell Medical Center in Libertyville. Prosecutors said she is in critical condition after the unprovoked attack, adding that she would have died if the Good Samaritan had not intervened.
Police arrested Link on the scene, charging him with attempted murder and several counts of aggravated battery.
"It's just bizarre. Never heard anything like it," said Rick Wiegman, a neighbor.
Police said officers later found the suspect's dog nearby and took him to animal control. During his initial court appearance, Link appeared from his jail cell, speaking mostly gibberish.
Prosecutors say Link told police he attacked the woman because he was "an angel of death."
Link repeatedly interrupted and swore at Judge Michael Chmiel, prompting him to delay the hearing.
Chmiel resumed the initial appearance after transferring Link to a more secure courtroom. He ordered him to remain in custody in McHenry County.
Anyone with information is asked to call the McHenry Police Tip line at (815) 363-2124. All calls are anonymous.