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Ross D. Franklin, Associated Press
As dozens protesters shout, Tia Oso of the National Coordinator for Black Immigration Network, center, walks up on stage interrupting Democratic presidential candidate, former Maryland Gov. Martin O'Malley, right, as moderator Jose Vargas watches at left, during the Netroots Nation town hall meeting, Saturday, July 18, 2015, in Phoenix.

PHOENIX — Former Maryland Gov. Martin O'Malley has been confronted at the annual Netroots Nation convention by protesters against police brutality.

As the crowd chanted, "Black lives matter," one of their leaders has taken over the stage during O'Malley's interview at the conference of liberal activists and bloggers in Phoenix.

O'Malley has defended his record. He required police departments to report all police shootings and to set up civilian review boards. The former mayor of Baltimore faced criticism after unrest broke out in his home city after an African-American man, Freddie Gray, died while in police custody in April.

The demonstrators later briefly disrupted Vermont Sen. Bernie Sanders and heckled him during his appearance at the convention. Democratic front-runner Hillary Rodham Clinton did not attend, citing a scheduling conflict.