(CNN) One of the officers had been on the job four days. One was on his third shift ever. And Derek Chauvin, who pressed his knee into George Floyd's neck for nearly nine minutes, was the field training officer for one of them.
Chauvin, J. Alexander Kueng, Thomas Lane and Tou Thao were responding to a call about a $20 counterfeit bill on May 25 when they detained Floyd, who died while in custody.
The four officers were fired and are now facing charges in Floyd's death.
Here's what we know about their role in Floyd's arrest as well as their lives before and while they were on the force, based on their personnel files.
What he did: Derek Chauvin, 44, pressed his knee into George Floyd's neck while Floyd was lying on the street.
The charges: Chauvin was charged on Wednesday with a new, more serious count of second-degree murder. He had previously been charged with third-degree murder and second-degree manslaughter.
The second-degree murder charge says he killed Floyd "without intent" in the course of committing assault in the third degree, according to an amended complaint.
Chauvin was arrested last week and is being held at a Minnesota Department of Corrections facility in Oak Park. His bail was increased to $1 million Wednesday, court documents show.
Background: Chauvin was a police officer with the Minneapolis Police Department for nearly 19 years.
He was the subject of at least 18 prior complaints and only two were "closed with discipline," according to a department internal affairs public summary.
The heavily redacted personnel files released by police only detail a 2007 complaint from a woman alleging that Chauvin had pulled her from her car, searched her and placed her in the back of a squad car for going 10 miles an hour over the speed limit.
An investigator found that Chauvin "did not have to remove complainant from car" and that he could have interviewed her outside the vehicle. The report noted that there was no audio of the incident and the dash came in Chauvin's car was turned off.
Chauvin admitted that he did not check to see if the dash cam in his cruiser at the start of his shift and left a microphone in the squad car during the traffic stop, the report says. He received a letter of reprimand and a notice of suspension for the incident, the documents show.
His files also include recommendations that he be given the department's medal of valor for his actions in two incidents. One involved shooting a man who pointed a shotgun at officers and another involved shooting a man suspected of a violent domestic assault, according to the personnel file.
When Chauvin applied for a job with the police department, he said he served in the US Army as a member of the military police and had worked as a custom protection officer for security services company. The files note Chauvin worked for McDonald's and another restaurant in the mid-1990's.
Chauvin was initially hired as a community service officer in January 2001 and served for about eight months before he was promoted to police officer, the personnel files show.
What he did: J. Alexander Kueng, 26, helped restrain George Floyd along with Derek Chauvin and Thomas Lane.
The charges: Kueng was charged Wednesday with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter.
He was arrested Wednesday and is being held on $1 million bail, county jail records show.
His background:
Kueng was hired as a police officer with the Minneapolis Police Department in December. He joined the department as a cadet in February 2019.
He had no prior complaints. When Floyd's death took place, it was Kueng's third shift as a police officer, said Thomas Plunkett, his attorney. Chauvin was Kueng's training officer, according to Plunkett.
He earned a bachelor's degree in sociology from the University of Minnesota, his personnel file says.
In his job application, Kueng said he worked as an asset protection detective for Macy's from 2014 to 2017 and in a temporary job with Target. He listed that he can speak, read and write Russian.
What he did: Thomas Lane, 37, helped restrain George Floyd, along with Derek Chauvin and J. Alexander Kueng.
The charges: Lane was charged Wednesday with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter.
Lane was arrested Wednesday and is being held on $1 million bail, county jail records show.
His background:
He joined the police department as a cadet in February 2019. He didn't have a history of complaints. Lane had been on the police force for four days when Floyd died, according to his attorney Earl Gray. Lane was "doing everything he thought he was supposed to do as a four-day police officer," Gray said.
After earning a bachelor's degree in criminology from the University of Minnesota in 2016, Lane worked as a juvenile corrections officer for Hennepin County and as an assistant probation officer.
He previously worked as a server and bartender at different restaurants and was a sales associate at Home Depot, according to his police job application. Under volunteer experience, Lane listed that he helps Somali youth in the Cedar Riverside neighborhood with their homework and tutors them in science and math activities.
What he did: Tou Thao, 34, stood near the other officers as they restrained George Floyd.
The charges: Thao was charged Wednesday with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter.
Thao, along with Kueng and Lane, was taken into custody Wednesday and is being held on $1 million bail, county jail records show.
His background: Thao had been a police officer with the Minneapolis Police Department since 2012.
He had six complaints filed with internal affairs, one of which was still open, according to a Minneapolis Police Department internal affairs public summary. The other five were closed without discipline.
Before becoming a police officer, Thao worked as a security guard, a stocker at a grocery store and a trainer at McDonalds. He attended the North Hennepin Community College and was pursuing an associate degree in law enforcement but didn't graduate, his personnel file shows.
Thao listed that he can speak Hmong. Minnesota has a large Hmong population.