CHICAGO (CBS) — A Chicago Police officer who announced last week that he was quitting the Fraternal Order of Police responded on Wednesday to critics who questioned his motives.

Officer Julius Givens issued the letter to FOP Lodge 7 President John Catanzara Jr. on Monday, June 29, and also published it on Medium.>/a> He took issue specifically with a comment Catanzara made in an interview with Bob Sirott on WGN Radio last month. Sirott asked Catanzara what he thought about seeing “good cops kneeling, marching, praying, crying” among peaceful protesters.

Catanzara’s response with which Givens took issue was, “Any member of Lodge 7 who is going to take a knee and basically side with protesters while they’re in uniform will subject themselves to discipline in the lodge up to and including expulsion from Lodge 7.”

“John, I am bewildered that given your position as the leader of one of the most powerful unions in the United States, that you would respond in such a manner. To hear the cry of the people we serve and ignore it is a crime against humanity,” Givens wrote.

Givens also took issue with Catanzara’s comments to Fox News host Eric Shawn, in which Givens said the union president blames “parents and lack of time spent in jail for the shocking numbers of gun related violence in our city.

“And while I agree that our criminal justice needs major improvements I was dispirited that not one time did you mention decades long policies such as: the war on drugs, redlining, access to quality education and healthcare at all stages of life, and other systematic policies of oppression,” Givens wrote. “To ignore these realities, at a time when children are dying in the streets, is to be indifferent to justice.”

Givens wrote that the police are not the problem, but could be part of the solution to the “painfully high issue of gun violence.

“However, we can not alienate ourselves from the people we serve with a hostile law and order approach to policing. This puts us in a losing position and I came on this job to win, just like the thousands of my colleagues,” he wrote.

He added, “The greatness of our city lies in its diversity. If Lodge 7 can realign their compass to that of the public we serve and its member’s I’d be happy to rejoin at a future date.”

On Wednesday, nine days after the letter was published, Givens issued a news release saying had now signed his separation papers and was no longer a member of the FOP. He said it would not be appropriate to critique the union moving forward since he has now left it, but he did respond to critics who had taken issue with his letter.

He addressed three specific “common themes” – first, a criticism that he does not qualify as “the police” because he has not been with the department long enough to speak out

“To them I say, look at the data. The most challenging problem for law enforcement in our city is gun violence. To date, I have the most gun recoveries of all three patrol-watches in my district this year — each recovery self initiated. The most recent came off of an attempt murder offender trying to flee. I chased him and arrested him just minutes after the shooting,” Givens wrote. “While there are many aspects to policing, violent crime and guns is where I focus my attention. Very few things destroy a family faster than a speeding bullet.”

Givens said others had taken issue with his issuing a public separation letter and had claimed he has a “hidden agenda.”

“Let me be clear, my agenda was this: first, to make public that the FOP in its current form does not represent me. Second, to confirm my position to my colleagues. Last and most important, to stand on the right side of history,” he wrote.

Thirdly, Givens wrote, some people have said the FOP is “part of a much larger system and cannot be changed.”

“To these folks I remind them that we reached for the stars and landed on the moon – that the imagination of the American people and the moral courage of free men and women have always won the day,” he wrote.

Givens reiterated that he would be glad to rejoin the FOP “if they realign their compass to that of the 2.7 million people we serve,” and asserted that he does believe that is possible.

“I spent many years as a knucklehead — in and out of jail, kicked out of classes, dishonest to significant others — you name it, I did it. It is a history I am not proud of, but a history I cannot deny. So, here is the good news: change is possible for all of us — especially those we encounter everyday from an enforcement perspective. Those, who like me, are not as bad as their worst day may portray,” he wrote. “To the hundreds of my colleagues who have reached out in support, thank you! I hear you. Continue to do the work of ensuring healthy and safe communities. This summer is giving us quite the fight.”

Addressing his colleagues on the police force, Givens wrote that it was not a battle against them or the work that police officers do.

“To everyone else, adult and child alike — I encourage you to find the greatest wall, take your hat off, and throw it over. It is in the exploration to retrieve your hat that you — whoever you may be and with whatever few resources you have — will move our country forward. Be bold and courageous — courage is the greatest virtue of them all — it guarantees all the rest. Bet on yourself,” he wrote. “You may fail, but you’ll live.”