In a heated exchange between Republican presidential front-runner Donald Trump and rival Jeb Bush during Saturday night's GOP debate, Trump accused former President George W. Bush of failing to keep the country safe on 9/11 and deliberately lying the public into the war in Iraq.

CBS debate moderator John Dickerson asked Trump if he still believes, as he said in a 2008 interview, that George Bush should have been impeached after it was discovered that former Iraqi leader Saddam Hussein did not have weapons of mass destruction, as the Bush administration claimed hundreds of times in the lead-up to the war.

In an apparent attempt to dodge the question, Trump noted that he is a businessman and it's his responsibility to "get along with everybody."

The audience, who minutes before Trump had accused of being establishment donors, began booing and forced a more thorough response, noted Policy Mic.

"Obviously the war in Iraq was a big fat mistake," Trump said.

He then reminisced about Jeb Bush's struggle last year to defend his brother's decision to go to war with Iraq. Jeb Bush initially said in May that if he were president, he would have authorized the Iraq war even if he knew what we know now. A few days later, he changed course and denounced his brother's invasion, admitting that it was based on incorrect information and was therefore a mistake.

"It took him five days, he went back - it was a mistake, it wasn't a mistake - it took him five days before his people told him what to say and he ultimately said it was a mistake," Trump said during the debate.

Trump continued: "We spent $2 trillion, thousands of lives, we don't even have it. Iran has taken over Iraq with the second largest oil reserves in the world. Obviously, it was a mistake. George Bush made a mistake. We can make mistakes, but that one was a beauty. We should have never been in Iraq. We have destabilized the Middle East."

Dickerson asked again whether Trump thought George Bush should have been impeached for the war.

"You can do whatever you want. I want to tell you. They lied. They said there were weapons of mass destruction. There were none. And they knew there were none. There were no weapons of mass destruction," Trump said.

Jeb Bush asked if he could respond to the criticism of his family and said, "So here's the deal. I'm sick and tired of Barack Obama blaming my brother for all of the problems that he's had."

"And frankly, I could care less about the insults that Donald Trump gives to me. It's blood sport for him. He enjoys it and I'm glad he's happy about it," Bush said. "I am sick and tired of him going after my family. My dad is the greatest man alive in my mind. While Donald Trump was building a reality TV show, my brother was building a security apparatus to keep us safe, and I'm proud of what he did."

Trump then interrupted with the bombshell: "The World Trade Center came down during your brother's reign. Remember that. That's not keeping us safe."

Watch the exchange below.