gunman, 25-year-old micah xavier johnson targeted white officers in revenge. [ gunfire ] he was killed by police during a standoff. today at a memorial for the fallen officers, mayor mikelings urged his city to unite. >> it's all about race. it's all about race. let's get over it. build the bridge, and let's get over it. >> there's so much hate, evi evilness towards each other. it's just, it's just ugly. >> you know what? there's a lot of people that support our cops. there's a lot of people that support everybody, because in the end of the day, it's all lives matter. >> the pain. >> reporter: the pain here is felt by even the youngest. >> hurt right now. >> reporter: it's also the youngest who are providing comfort. >> want to give him a hug? >> reporter: officer ira carter knew the fallen officers. >> you gotta start and grieving process and understand which direction we got to go and pray and hope this doesn't happen in america again. >> reporter: the ongoing investigation here is massive with streets like this one closed possibly into next week. reena, detectives have already interviewed more than 200 people. >> reena: manual bojorquez in dallas, manuel, thank you.