One recruit, identified as Alejandro Martinez, has suffered setbacks in his recovery that left him in grave condition, according to the Los Angeles County Sheriff's Department. Additional details about his injuries were not released.
The three others, who are part of the Sheriff's Academy Class #464, were still in critical condition. The department said the rest of the law-enforcement recruits have been released from the hospital.
Authorities arrested a 22-year-old driver who they believe intentionally slammed into the group of about 75 law-enforcement recruits who were on a run as part of a training exercise. The academy class included sheriff's and other police agencies' recruits.
Whittier crash: Suspect's social media being searched for any possible 'anti-police' views
Nicholas Joseph Gutierrez was arrested Wednesday on suspicion of attempted murder on peace officers after 25 recruits suffered injuries ranging from minor to critical, according to the sheriff's department.
Investigators have not elaborated on what evidence they had to warrant the arrest, and they released Gutierrez the following day. Sources told ABC News the charge is based on statements made by recruits and other witnesses who were on scene at the time of the crash.
Sheriff Alex Villanueva previously said the crash was an accident. Authorities later clarified that was based on preliminary information, as they continued to investigate.
Video shows SUV slam into recruits
Video shows graphic view of driver slamming into law-enforcement recruits in Whittier
The incident unfolded early Wednesday morning in the South Whittier area near Mills Avenue and Trumball Street.
Surveillance of the incident recorded from a nearby backyard shows the group of recruits running in tight formation along the side of the road, escorted by two cruisers at the back of the columns.
The SUV is driving on the left side of the road and does not appear to slow down or swerve as it heads directly into the jogging group.