A former New York City police commissioner called out District Attorney Alvin Bragg for his "radical" approach to handling crime in the Big Apple, citing his most recent handling of a serial stabbing that killed three innocent bystanders.

The Guardian Group CEO Ray Kelly revealed why he believes Bragg is the "most radical" district attorney the city has ever seen, pointing out that Bragg advertised his soft-on-crime approach as soon as he was voted into office. 

"Mr. Bragg is not reasonable," Kelly told "Fox & Friends" co-host Brian Kilmeade on Wednesday. 

"He is… a believer in the most radical of approaches. As a matter of fact, the first day in office, he gave us a manifesto over what he's not going to do. One of them being that he is not going to arrest people for fare-beating, which, by the way, the MTA says that's where they're losing three quarters of $1 billion a year on this, and that's why we have congestion pricing because of District Attorney Bragg."

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Police arrested 51-year-old Ramon Rivera, a career criminal, earlier this week after he allegedly went on an unprovoked stabbing spree in the city, killing three people. 

Rivera, a homeless man, has eight prior arrests and had been released from jail just weeks before the fatal knife-wielding attacks. 

"That type of confrontation happens every day on the streets of New York, particularly in midtown Manhattan," Kelly said. "People are out threatening those who [are] just going about their their business. Sometimes it results in assaults. Sometimes it doesn't, but this is still a major problem."

"We've got to get these types of people off the streets, yet there's no realistic movement to do that now," he continued. 

Meanwhile, Bragg's office has tried, unsuccessfully, to prevent records related to Jordan Neely's alleged drug abuse and mental illness from being considered in Daniel Penny's New York City manslaughter trial. 

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Forensic psychiatrist Dr. Alexander "Sasha" Bardey revealed on the witness stand Tuesday that Neely had been hospitalized more than a dozen times for psychotic episodes and abusing synthetic marijuana before his death on a Manhattan train last year. 

Neely had a documented history of paranoid schizophrenia, Bardey testified, after reviewing thousands of pages of the man's medical records dating back to 2015, and considered his case to be among the most severe he has seen. 

"Interestingly, in the Penny case, there was a testimony yesterday from somebody from the medical examiner's office that said they went… [through] literally thousands of pages of Mr. Neely's records as far as his psychiatric problem," Kelly said. "So, yeah, and the district attorney, of course, doesn't want to have that admitted, so it kind of highlights the dichotomy, and I certainly hope there's not a racial component involved in this case."

"Mr. Penny, was a hero by anyone's definition," he continued. "If any of us were trapped in a situation like that with the man who obviously is... saying he's going to murder people, we want that type of intervention. And I also thought that he held on to Mr. Neely because he was waiting for the police to come. And when the police did arrive, that's when he let him go."

Penny faces up to 15 years in prison if convicted on the top charge of manslaughter. He also faces a lesser charge of criminally negligent homicide.

Fox News' Michael Ruiz and Grace Taggart contributed to this report.