Two of the men were arrested after being pulled over with the injured man in their car.
"Whether they were trying to get him to the hospital, I don't know," said Michelle Van Der Linden, spokeswoman for the Chino Police Department.
Chino investigators were contacted by Tustin police officers on Tuesday morning alerting them to a crime that reportedly took place in Chino, officials said.
Tustin police officers stopped a vehicle on Tuesday and found one of the passengers had a severe head wound.
Two other people, including the driver, were in the vehicle with the injured man but they were not hurt.
The injured man - 22-year-old Aaron Vankorlaar of Fontana - was taken to an Orange County hospital where he was listed in critical condition.
Through an investigation, Chino police officers learned the Vankorlaar had been attacked with a blunt object in the 12100 block of Ramona Avenue in Chino.
Blake Pelmon, 20, of Rancho Cucamonga as well as Seth Coleman, 18, and Jacob Perry, 20, both of Fontana, were arrested on suspicion of attempted murder, robber and conspiracy.
Detectives were able to identify Coleman, Perry and Pelmon as the alleged attackers.
The investigation is ongoing and anyone with information regarding this incident is asked to call the Chino Police Department at 909-628-1234.