South Bend, Indiana (CNN) Pete Buttigieg appeared at the South Bend Police Department Wednesday to reassure residents that he has his police department under control after an officer involved shooting left a 54-year-old black man dead early last Sunday morning.

The mayor, who has taken days away from his presidential campaign to respond to the shooting, described the fallout as "very challenging" as he swore in new South Bend Police Department recruits. Buttigieg urged the new officers not to pretend the tension around policing "is unrelated to race and racism" and he implored them to connect with residents in South Bend, including the city's racial minorities.

But a key problem with the city's police department, something that activists have lamented for years, was staring back at the mayor: All six of the new officers coming into the South Bend Police Department are white.

The most recent officer involved shooting -- which has South Bend on edge -- underscores persistent tension between the city's African American community and its police department, which has grown less diverse during Buttigieg's tenure. Accusations of poor leadership have hampered both of the mayor's two hand-picked police chiefs and admissions of violence by officers have cost the city thousands in settlements.

Interviews with a dozen former South Bend police officers and activists from the city back up that tension, highlighting the tumultuous relationship the police department has had with many residents during Buttigieg's eight years as mayor. The strain is more resonant now as Buttigieg mounts a once-longshot bid to jump from mayor of a 100,000-person city to President of the United States -- using his mayoral record as a key validator.

"He (Buttigieg) took a passive approach with the police department," said Derek Dieter, a 39-year veteran of the South Bend Police Department who also spent 12 years as a member of South Bend's city council, know as the Common Council. "I've gone through four or five mayors, but this has taken a certain turn. Qualified minority officers leave, because there is no avenue of advancement or promotion."

Dieter and Buttigieg have disagreed with one another on issues in South Bend for years. Dieter lost his 2015 bid to be the South Bend clerk to Kareemah Fowler , the candidate the mayor backed.

Buttigieg has worked on police issues during his eight years in office. As Mayor, Buttigieg's campaign aides noted, Buttigieg adopted a new duty manual guiding police conduct, launched an online police transparency portal to provide information about the police department to residents and introduced body cameras for all officers. Buttigieg, who appoints people to the Board of Public Safety , often mentions that the body is majority minority, something he has prioritized.

But concerns from African American activists grew louder this week when it was revealed the officer involved in the shooting was Sergeant Ryan O'Neill, a veteran of the South Bend Police Department who has been accused by both officers and residents he arrested of racist behavior. Some of those allegations were found to be "not sustained" by the Office of Internal Affairs, said Ken Garcia, spokesman for the police department, but complicating the matter was the fact that O'Neill's body camera was not turned on during the interaction that left the victim, Eric Jack Logan, dead after he was allegedly breaking into cars with a knife in hand. O'Neill was put on administrative leave after the shooting and the South Bend Police Department did not respond when asked to speak to the officer.

Buttigieg has said he is "extremely frustrated" that there is no body camera footage and ordered his police chief on Tuesday to ensure that cameras are on during all interactions with civilians.

"Sunday is just a reminder of how much work we have yet to be done," Buttigieg said Wednesday at the swearing in of new South Bend police officers.

But the shooting has reignited questions about how Buttigieg has handled the South Bend Police Department, including from activists who rallied in the city Monday night. And it has also put a spotlight on tension between Buttigieg and African Americans in the city he leads, an issue that could impact the mayor's now national profile.

"The problem is (Buttigieg) has an issue with people of color, that is why his campaign is not identifying those people of color," Rev. Sylvester Williams Jr. said during a vigil for the victim of the officer involved shooting. "He has people of color right here. We need more out of him. We need him to stick and stay, and not run away."

Changes in leadership

Democratic Presidential candidate and South Bend, Indiana Mayor Pete Buttigieg speaks to newly sworn in police officers on Wednesday, June 19, 2019, at the South Bend Police Department.

Buttigieg's first major decision as mayor came shortly after he took office in 2012 when he ousted the city's first black police chief. That decision was met with outrage from activists in the community and was compounded when Buttigieg subsequently named two white officers to lead the department.

Buttigieg asked his first police chief -- Darryl Boykins -- to resign over a complicated and contentious situation centering on a federal investigation into the contents of five tapes of recorded phone conversations inside the South Bend police department and allegations that the tapes contain racist comments about Boykins.

Buttigieg changed his mind, and demoted Boykins instead. But the entire situation -- which came to be known as the tapes case -- led to a series of protests against Buttigieg and created a level of distrust between Buttigieg and the African American community that hung over the young mayor's first term in office.

The divide grew when Buttigieg named two white officers to be the next police chiefs, including Ron Teachman, a white officer who has spent much of his career in New Bedford, Massachusetts, and was named police chief in South Bend in 2013.

"We've had 7 years of uncertainty when it started with the tapes," Oliver Davis Jr, a Common Council Member, said Monday. "When the mayor fired our chief and the way he degraded our chief was horrible ... that is the bottom line of what has caused these issues."

Boykins' ouster and Teachman's hiring, according to officers who worked under both men, depressed morale inside the department, especially among black officers. And questions about Teachman's leadership persisted after an incident at the Martin Luther King Jr. Recreation Center in South Bend on April 22, 2013, just three months after he became chief in January.

Teachman, according to Patrick Cottrell, the then-President of the South Bend Board of Public Safety, was at the recreation center with Lieutenant David Newton when a fight broke out outside the center. Newton responded to the fight, Cottrell said, but when he requested back up from Teachman, the police chief chose to remain inside the center and not respond to Newton's call for help.

Newton did not respond to repeated request for comment.

The Indiana State Police investigated the incident. The agency handed the results of the investigation to Buttigieg, but they were not made public, which left many in South Bend dissatisfied.

When reached on Sunday, the Buttigieg campaign said the report was not released because it involved a personnel matter. Buttigieg cleared the police chief of any wrongdoing and, according to local reports at the time, urged the police chief to ignore the controversy.

"Just wanted to send a word of encouragement," Buttigieg wrote in an email to Teachman, according to local reports . "I know that you will not let the nonsense aired in Council distract you from your great work."

"This was so over the top egregious because policemen and firemen that were regular guys, were suspended and fired for doing less than Teachman," said Cottrell, who resigned over Buttigieg's handling of the incident, according to his resignation letter obtained by CNN. "How can you discipline subordinates and not discipline the person who is supposed to be the leader? The mayor proved he wasn't a leader when he couldn't even do that."

Teachman did not respond to request for comment from CNN.

The issues under Teachman were broader than just one incident, though. Many officers, especially black officers, believed that their opportunities for promotion plummeted after the new chief was appointed. And that continued after Teachman resigned in 2015 to take a job in the private sector and Buttigieg hired Scott Ruszkowski, a white officer who is a 27-year veteran of the force and leads the department to this day.

Some of those complaints were documented in lawsuits, like one filed by Davin Hackett alleging racial and military discrimination and retaliation in a suit against the City of South Bend, Ruszkowski, and Teachman in 2017 -- after he spent 11 years working in the South Bend Police Department.

"I would rather work in a war zone than work in the South Bend Police Department," said Hackett, whose federal suit is pending against the city for military and racial discrimination. Garcia, the South Bend Police Department spokesman, declined to comment on the allegations, given the lawsuit is "ongoing" and the city "cannot comment on pending litigation."

Hackett is now running for a seat on South Bend's Common Council.

Buttigieg, asked by CNN on Saturday whether he believed the two men he appointed to lead the South Bend Police Department had done their job effectively, said that "there have been issues throughout my tenure."

"I think there's been a lot of good work. And I think there's a lot of good work yet to go," Buttigieg said. "We're going to be assessing all the steps that brought us to this point, and all of the things that we haven't gotten to where they need to be. And that's going to be a major challenge that the department faces."

He added: "We've taken a lot of steps that have I think, served us very well as a community. But obviously, when something like this (fatal shooting) can happen, when some of the questions that are being asked are there, we've not done enough, we've not gone far enough, we've not managed to decisively solve this incredibly challenging problem, and it will be on our agenda for as long as I'm there."

Minority officers decline by 50%

Under Buttigieg, the South Bend Police department has slowly -- but consistently - grown less diverse.

The department had 26 African American officers in 2014, according to news reports at the time, meaning a little more than 10% of the 253-officer department was black. There are now 13 black officers in the South Bend Police force, according to numbers released by the department, leaving the force 88% white and just over 5% black.

That steady decline in African American officers is opposite to the demographic makeup of South Bend. According to the 2010 census, the city is 26% African American.

Buttigieg was aware of the lack of diversity in the police force for years, and in an interview with CNN earlier this month, admitted that it was "one of the biggest pieces of unfinished business" he has left as mayor.

"We've undertaken a number of efforts to reach out and get more diverse applicants to begin with. We've even mapped out where we lose applicants," Buttigieg said. "But I'm not satisfied with where we are as a city in terms of the diversity of our police department. And it's something we need to keep pushing on."

But some in South Bend believe it is the way Buttigieg's police chiefs ran the department that has made it hard to keep minority officers.

"If you can't get along with minority people in your own town," said Dieter. "What makes you think you're going to get along with minorities in the rest of the country."

The many cases of Aaron Knepper

One issue that bewildered many former South Bend Police Department officers that CNN spoke to is how certain officers were reprimanded for infractions, while more violent officers were allowed to stay on the force.

And no officer better encapsulates those questions, according to former officers CNN spoke to, than Aaron Knepper, an officer who has a long history of excessive force allegations against him.

Knepper's history with controversy began in 2012, when he and two other officers -- according to news reports at the time -- punched, tased and detained DeShawn Franklin, then an 18-year-old high school student, after storming into his parents' home. The case was one of mistaken identity, however, and Franklin turned out to be the wrong person.

Franklin sued over the treatment, but in a ruling that drew national attention , a jury only awarded him $18. In response to the incident, a group of civil rights activists started a petition that asked Buttigieg to fire Knepper and publicly apologize to the Franklin family.

Later that year, Knepper and two other officers, according to local news reports at the time, forced Jonathan Ferguson, a 7-Eleven employee with learning disabilities, to swallow cinnamon on camera in retaliation for a complaint the clerk filed against the officers for declining to go after an alleged drunk driver.

Swallowing the cinnamon caused Ferguson to become ill and vomit for several hours, according to the news reports. Knepper and the other officers later posted the video on YouTube.

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The three officers were suspended for two days without pay and, after Ferguson sued, the city settled for $8,000 and made the officers delete the video.

"Obviously I'm not pleased," Buttigieg said at the time. "Look, anybody who represents the city needs to represent the city to the highest values. But there is a subset of those people, and those are the public safety officers, who actually have the name of our city stitched on their shoulders. And as such they need to be individuals who can be trusted at all times to do the right thing, especially when it comes to interactions with our most vulnerable residents."

But Knepper remained on the streets and proceeded to trigger public outcry in 2014, when the city had to pay a $15,000 settlement after an altercation Knepper had caused a local golf champion to be in the hospital for days -- and again in 2016 when Knepper was involved in an altercation with then Notre Dame football player Devin Butler. The football player would later plead guilty and apologize to the department.

Throughout it all, Buttigieg deferred to the police department and Board of Public Safety's decision to keep Knepper, despite a community led "Fire Knepper" campaign.

"I have to follow certain processes and procedures when it comes to hiring and firing of officers," Buttigieg said Saturday. "But what I'll say is that officers should be held to the highest standard, and that there's some behavior that simply can't be tolerated on the police department."

But the mayor's office also directed CNN to remarks Buttigieg made in 2016 about Knepper, where the mayor noted "a firing-level personnel decision is made by the Board of Public Safety" but that he accepted "responsibility for appointments to the Board of Public Safety and (police) chief."

Ruszkowski sent Knepper back on patrol in 2017, despite the calls for his ouster.

"I don't think this can be resolved by targeting any individual," Buttigieg said at the time. "It can only be resolved by making sure we have a higher level of trust in the community that's borne out by consistently positive behavior and consistently fair discipline."

Knepper was one of the responding officers to the fatal shooting this week, raising concerns for activists in South Bend. The controversial officer drove Logan to the hospital in his squad car, a decision the prosecutor investigating the case said was made in order to rush the shooting victim to the hospital. But activists were skeptical, given protocol is for officers to wait for an ambulance.

Asked about Knepper's history, Garcia said, "All incidents besides the Butler case were handled by previous chiefs. ... Chief Ruszkowski cannot retroactively discipline an officer for incidents previous chiefs already reviewed."

But Knepper's history of controversies with the department and lack of punishment angers and confuses his colleagues, according to CNN's conversations with officers. And many blame Buttigieg for not doing more.

"I don't know how they could get away with those things," said Cottrell, the former president of the South Bend Board of Public Safety. "I don't know how you justify that in your head, as chief, as mayor."