State investigators looking into the killing of George Floyd have requested the training records of all the former Minneapolis officers who were present, as well as access to surveillance footage that may have captured the encounter that sparked massive protests and fresh calls for reform of the city's police force.

In building their case against Derek Chauvin, the since-fired Minneapolis police officer who is charged with Floyd's death, special agents from the state Bureau of Criminal Apprehension (BCA) sought access to hospital and ambulance records, security camera footage from the hospital where Floyd died and records of the officers' de-escalation and first aid training.

"Part of the scope of the investigation is to examine the officers' use of force, and to corroborate statements of witnesses and officers," BCA special agent Matthew Lund wrote in a search warrant affidavit. "Therefore, documented verification is needed of the injuries and attempted medical intervention."

The BCA, which investigates most police shootings and in-custody deaths, made similar requests in the killing of Justine Rusz­czyk Damond.

"As a part of a thorough investigation, BCA Agents are requesting authorization to obtain personnel files to include pre-employment psychological records, all training records, and internal affairs files for the above listed officers," Lund wrote in another warrant. Investigators also sought access to the officers' lockers at the Third Precinct station.

Chauvin was charged Friday with third-degree murder and second-degree manslaughter, after he was recorded kneeling on Floyd's neck for nearly nine minutes, ignoring the handcuffed man's pleas that he couldn't breathe. A bystander recorded the encounter at E. 38th Street and Chicago Avenue on Facebook Live, where it has been viewed countless times.

What started as peaceful protests after the video spread has since erupted into rioting nationwide; dozens of buildings in Minnesota were looted or torched. Gov. Tim Walz called in the Minnesota National Guard to help quell the unrest. The protests prompted nighttime curfew orders in the Twin Cities and several other cities.

Chauvin is the first white officer in Minnesota to be criminally prosecuted in the death of a black civilian. The maximum sentence for third-degree murder is 25 years; the maximum for second-degree manslaughter is 10 years. The other officers involved — Tou Thao, Thomas Lane and J Alexander Kueng — were also fired but have not been charged.

According to the criminal complaint against Chauvin, police were called after Floyd was suspected of passing a fake $20 bill at the Cup Foods convenience store. Lane and Kueng approached Floyd, who was in a Mercedes-Benz with two other people. At some point, Chauvin and Thao pulled up to the scene. After ordering him out of the car, police were leading the handcuffed Floyd to a squad when he collapsed, and three of the officers got on top of him, authorities say. He died later at HCMC. The hospital has also been asked to turn over all video from its ER and the operating room from the time when Floyd was brought in, court filings show.

Lund filed a search warrant affidavit Monday afternoon for "all training records, specifically related to use of force, crowd control, crisis intervention/de-escalation and first aid" for the four officers.

He also sought the names of all instructors from Minneapolis police or externally who taught the topics to the officers, and copies of all training materials.

"As part of a thorough investigation, BCA agents are seeking these documents to provide a written record to the officers [sic] level of training and also to document techniques received during training," the affidavit said.

Authorities also requested access to Cup Foods' surveillance footage. A nearby restaurant, Dragon Wok, also had cameras that may have captured part of the incident.

Earlier this week, the FBI asked any witnesses who recorded footage of the encounter to turn it over to investigators.

In an unrelated incident, police are investigating the possible theft of a Minneapolis police bulletproof vest from the Third Precinct, which last week was overrun and torched by rioters. An investigator wrote in a search warrant affidavit that police received a tip that a man was sending pictures from his cellphone showing himself in a photo wearing the vest.

"The office where the Police Vest was taken from, contained items that include … classified case files of gang members, classified information on ongoing criminal cases, property such as Police radios/charges/GPS trackers, vehicle keys, a safe, scales, police bags, police vests, police jackets, police uniforms, documents containing police information/reports, etc.," the affidavit read.

Police sought the warrant to search a 38-year-old suspect's home and workplace in northeast Minneapolis. Court documents show that the warrant was executed and nothing was taken.

According to the affidavit, the video posted online allegedly showed the man wearing a vest emblazoned with the name of Minneapolis police officer J.B. Werner while standing next to a wall with "dozens of tools hanging on the wall."

Jeff Werner, a decorated 20-year veteran in the department, worked in the weapons unit, which works closely with the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.