Sen. Bernie Sanders (I-VT) slammed former Maryland governor Martin O’Malley at Saturday night’s Democratic presidential debate at Drake University in Iowa: “With all due respect, I think it’s safe to say Baltimore is not now one of the safest cities in America.”

The rebuke came during an exchange over gun control, when former Secretary of State Hillary Clinton brought up Sanders’ vote decades ago against the assault weapons ban–an attack that worked for her in the first Democratic debate in Las Vegas last month.

O’Malley piled on, talking about the gun crontl measures he had taken in Maryland in the wake of the 2012 mass shooting at Sandy Hook in Newtown, Connecticut.

Sanders seemed irritated by it all, and hit O’Malley with a comeback that referred to the recent rise in violent crime in Baltimore, which occurred in the wake of riots after the death of a black man, Freddie Gray, while being transported to a police station.

The Baltimore upheaval helped fuel the “Black Lives Matter” movement, which started in response to the shooting of unarmed black teenager Michael Brown in Ferguson, Missouri as he charged a police officer.

Initially, Black Lives Matter considered Sanders unresponsive to their concerns. However, in the past few weeks he has apparently emerged as the movement’s favored choice for president, as he has linked his proposal for free college tuition to the campus protest groups aligned with Black Lives Matter.