U.S. Republican presidential contender Donald Trump is upset that he wasn't interviewed with by Florida police in the aftermath of the incident that led to his campaign manager being charged with simple battery.

Trump, in an interview with Fox News Channel's Sean Hannity to air Tuesday night, said he thought it was "very unjust" that "nobody" from law enforcement called him after the early March incident.

A  reporter accused Trump's campaign manager, Corey Lewandowski, of grabbing her. Lewandowski turned himself into Jupiter, Florida, police Tuesday.

Trump played up his connections in the Florida town, where he owns a resort, while expressing his puzzlement over the police department's actions. He suggested that his staffer acted to protect him and vowed not to fire him.

"You know, they're chopping off heads, they're drowning people in the Middle East," Trump said. "We're going to destroy a man's life?"

Trump said he doesn't "discard people" and called the situation "very unfair" to Lewandowski, one of his closest advisers. He said he hopes the matter doesn't change Lewandowski's role on his campaign.

A report from the Jupiter Police Department in Florida said Lewandowski, 42, is accused of intentionally grabbing and bruising the arm of Michelle Fields, a former reporter for the conservative news outlet Breitbart, at a Trump campaign event on March 8.

The police department also released a video showing the incident between Fields and Lewandowski.

"Lewandowski grabbed Fields's left arm with his right hand causing her to turn and step back," reads the police report. Fields showed police her left forearm which "appeared to show a grabbing-type injury," according to the investigating officer.

At the time, Lewandowski called Fields "delusional" and said he never touched her. He has since retained a Florida attorney who said Tuesday there would be no further comment.

Unlike previous videos released by news networks which were at the campaign event, the new video is not obscured by people. The video shows Fields walking alongside Trump and then Lewandowski grabbing her arm and pulling her backward.

"Mr. Lewandowski was issued a Notice to Appear and given a court date. He was not arrested," Trump's campaign said in a statement. "Mr. Lewandowski is absolutely innocent of this charge. He will enter a plea of not guilty and looks forward to his day in court. He is completely confident that he will be exonerated."

Trump fires back

Speaking to reporters on his airplane in Wisconsin Tuesday, Trump said Lewandowski has been "very seriously maligned," and vowed to stand by him.

"I can't just stand by and watch a man's life be destroyed," Trump said. "I'm sticking up for a person because I'm not going to let a person's life be destroyed. No jury, in my opinion, would convict a man and destroy a man's life over what you witnessed.

"How do you know those bruises weren't there before?" the New York businessman charged.

The Trump campaign said Lewandowski would plead not guilty and "is completely confident that he will be exonerated."

Trump on Tuesday reversed a previous position that the incident never happened, suggesting instead that Lewandowski was trying to block Fields from "grabbing and asking questions."

"She was grabbing me. Does that mean I'm supposed to file charges against her?" Trump said to reporters.

The anti-Trump Our Principles PAC has been airing an ad featuring news clips of violence at Trump rallies and playing audio of the Republican front-runner saying of a protester, "I'd like to punch him in the face."

The same ad includes images of Fields's bruised arm and a Fox News interview in which she says that Trump's campaign wasn't telling the truth about what happened to her.

"The police in Jupiter, Florida, have clearly seen what Donald Trump refuses to acknowledge: his campaign manager battered a woman and caused serious bruising," said Our Principles PAC leader Katie Packer. "In any job in America this would be grounds for firing. Instead, Donald Trump has praised him."

Under Florida law, battery is defined as intentionally touching or striking a person against their will. For a first offence, it is a misdemeanour in the first degree, which carries a maximum sentence of one year in prison or a fine of $1,000.

A court date was set for May 4, according to the police report. Jupiter police said Lewandowski turned himself in, and he was issued a notice requiring him to appear in court and then released. He was not booked into the jail.

Four journalists from the conservative news website, including Fields, quit earlier this month in protest after the assault, saying their news organization was not supporting them and accused Breitbart of bending to pressure from the Trump campaign.

Trump's rallies across the United States have been marked by rowdiness and physical contact between protesters and either his supporters or security personnel.

USA-ELECTION/TRUMP

Corey Lewandowski, right, campaign manager for Republican U.S. presidential candidate Donald Trump, centre, are seen with Breitbart News reporter Michelle Fields, left, after a news conference held at Trump's National Golf Club in Jupiter, Fla., on March 8, 2016. Lewandowski was charged with battery for his interaction with Fields at the event. (Joe Skipper/Reuters)

Cruz, Kasich weigh in

Ted Cruz, one of Trump's rivals in the Republican presidential nomination race, told reporters while campaigning in Wisconsin that the charges against Lewandowski reflected the "abusive" culture of the Trump campaign.

"When you have a campaign that is built on personal insults, attacks and now physical violence, that has no place in our campaign, it has no place in our democracy," Cruz said.

John Kasich, also running for the presidential nomination on the Republican side, said he considered such behaviour "totally and completely" inappropriate.

"If it was me, if I were in this circumstance, I would take some sort of action, either suspension or firing," Kasich told reporters in Wisconsin.

Kasich's chief strategist John Weaver said Lewandowski would've been fired "long ago" had he worked for Kasich. He added that campaigns reflect the values of a candidate.

With files from CBC News and The Associated Press