The three Democratic presidential candidates on the stage. AP Photo/Charlie Neibergall For five minutes, the three Democratic presidential candidates got into a heated brawl over gun control.

Democratic front-runner Hillary Clinton criticized Sen. Bernie Sanders (I-Vermont) for granting "immunity" to the gun lobby by supporting a controversial gun law called the Protection of Lawful Commerce in Arms Act, which shelters most gun manufacturers and distributors from most legal liability if sued by victims of gun violence.

"That was a terrible mistake," Clinton said.

Former Maryland Gov. Martin O'Malley (D) touted the gun-safety legislation he passed during his time in office, and he criticized both Sanders and Clinton on the issue.

O'Malley hit Sanders for his support for the PLCAA. Then he turned to Clinton, saying the then-Senator sounded like "Annie Oakley" during her previous presidential bid, a reference to President Barack Obama's criticism of Clinton in 2008.

“Secretary Clinton, you've been on three sides of this. In 2000, you said we need robust regulations," O'Malley said, referencing gun control measures. "Then, in 2008 you were portraying yourself as Annie Oakley, and saying that we don't need those regulations on the federal level. Now, you're coming back around.”

Sanders defended his record, saying he supports universal background checks and would "re-examine" his vote for the PLCAA. He also hit back at O'Malley, pointing out that Baltimore has a high rate of gun violence.

"With all due respect, it's fair to say that Baltimore is not now one of the safest cities in America," Sanders said.