Department of Homeland Security Secretary Jeh Johnson said Sunday he is “concerned” about race relations in the U.S., following last week’s shooting in Dallas and separate incidents in which two black men were shot and killed by police.

“I am concerned, Chuck,” Johnson told NBC News’ Chuck Todd. “I think at a time like this when tensions are high, in the wake of events in Dallas and Baton Rouge and Minnesota and elsewhere, it’s important to remember that just as the shooter on Thursday night is not reflective of the broader movement to bring about change in police practices that any police officer who engages in excessive force is not representative of the larger law enforcement community.”