TULSA, Okla. — After he sold his insurance company for around $6 million, Robert Bates sought to return to a profession he tried for a year in his early 20s: law enforcement.

Bates — the 73-year-old Tulsa County volunteer deputy accused of shooting an unarmed suspect to death while the man was being held down by others — began a law-enforcement career back in 1964, when he attended the Tulsa police academy. He served in the city police department only briefly, until the end of 1965, according to the agency.

That's where Bates' path becomes clouded. It's not clear why he left the police force, but 35 years later, he reconnected with law enforcement, becoming a generous donor to the Tulsa County Sheriff's Office, a campaign manager for the sheriff and a reserve deputy.

Those close ties have raised questions about whether Bates was essentially paying for the privilege of working alongside real officers and whether he had received proper training and certification to perform law-enforcement duties, including carrying weapons.

Bates, who has been charged with second-degree manslaughter, went on national television Friday to counter criticisms of his qualifications.

Speaking publicly for the first time since the April 2 shooting, Bates told NBC's "Today" show that characterizations of him as a wealthy donor who paid to join the force are "unbelievably unfair."

The Tulsa Police Department has not explained why Bates abandoned police work or responded to repeated requests from The Associated Press for documents related to his departure in 1965.

After Bates left the police department job, his path fades again for more than a decade.

In 1977, he started his own insurance company. By the time he sold it in 1999 to the North American Insurance Agency Inc., it was worth nearly $6 million, according to court records. That's when Bates began moving back into the world of law enforcement.

He served as a civilian volunteer and rode along with officers in the marine patrol division of the Indian River County Sheriff's Office in Florida from 2000 to 2001, but his role did not allow him to be involved in criminal enforcement, according to Sgt. Thom Raulen, a spokesman for the office.

Florida property records show Bates owns a luxury home in a gated community on Vero Beach. Under Florida appraisal standards, it was valued at $610,400 last year, down from nearly $1 million before the 2008 recession.

Six years after his volunteer work in Florida, Bates became an advanced reserve deputy for the Tulsa County Sheriff's Office and began working with the violent crimes and narcotics task force in 2008, according to paperwork he submitted after the shooting.

In the paperwork, Bates wrote in that he attended "numerous" schools and seminars related to drug investigations and apprehending drug-trafficking suspects. He stated that he attended a five-day homicide-investigation school in Dallas and received training from the Maricopa County Sheriff's Office in Arizona.

But a spokeswoman for the Maricopa County Sheriff's Office and Dallas County Sheriff's Department spokesman Raul Reyna said their agencies have no record of Bates receiving any training there.

Advance reserve deputies in Tulsa County are required to complete 480 hours of training, but a sheriff's office spokesman said Friday the sheriff has the right to waive some requirements based on previous experience and training.

The Oklahoma agency that certifies officers says weapons certifications cannot be waived, and spokesman Maj. Shannon Clark said Friday he does not know if the sheriff waived requirements for Bates. Clark said the instructor who qualified Bates on the weapon he was carrying is no longer with the department and that officials have not had time to locate all of Bates' training records.

Bates has donated tens of thousands of dollars in cars, SUVs and equipment to the Tulsa County Sheriff's Office over the past 10 years, records released by the office show.

His donations include a $25,000 Chevrolet Tahoe in 2010 and a high-tech forensic camera and lens kit worth more than $5,000 in 2009. He also gave $2,500 in 2012 to the re-election campaign of Sheriff Stanley Glanz — the largest donation the sheriff received during that cycle, according to Oklahoma Ethics Commission records.

In addition, Bates donated his time, participating in at least 100 assignments as a member of the task force.

His close ties with the sheriffs' offices in Florida and Oklahoma have been targeted by critics who say Bates essentially paid for access to come along on missions.

At least 200 protesters assembled late Friday near the county courthouse, calling for Glanz to resign and an outside agency to examine his office's handling of the shooting. From there they marched to the sheriff's office.

Lakeisha Carroll said she'd like to see greater transparency from the sheriff's office about the shooting.

"We can't get any answers," the Tulsa resident said. "That means you're hiding something, you're trying to get your stories straight."

A spokesman for the sheriff's office declined to comment on the calls for Glanz's resignation.

Bates' attorney, Clark Brewster, said his client's actions have been twisted.

"This is a good son-of-a-gun," Brewster said Thursday in an interview. "I don't know how they can paint him as sinister."

He also disputed a report in the Tulsa World that sheriff's office supervisors were ordered to falsify his training records.

Bates insisted Friday that he is certified to be a reserve deputy.

"I have it in writing," he said on "Today."

Bates has not responded to requests to provide supporting documents to the AP.

Video released by the sheriff's office shows Eric Harris running and deputies restraining him after an alleged undercover gun deal. Bates has said he shot the 44-year-old suspect after mistakenly grabbing his handgun instead of his stun gun.

"You must believe me, it can happen to anyone," Bates said Friday.

Video also captured Bates apologizing for shooting Harris, who was being detained on suspicion that he tried to sell guns to an undercover officer.

"Oh, I shot him! I'm sorry," Bates said.

Clark said Harris' death prompted an evaluation of the reserve deputy system.

Bates said the shooting was accidental and apologized to Harris' family.

"I rate this as No. 1 on my list of things in my life that I regret," he said.

Associated Press Writer Allen Reed contributed to this report from Little Rock, Arkansas.