the democratic presidential candidate said he should have paid more attention to the warning signs. i must confess i was dumb i should have listened to the symptoms so if there is any message that i hope we can get out there is that i want people to pay attention to their symptoms. and we re going hear much more from senator sanders in an exclusive sit-down interview with our own harry smith that s tomorrow right here on nbc nightly news. in dallas, the suspect is in custody and police are searching for two more men in the killing of a witness who testified in the murder trial of former dallas police officer amber guyger our morgan chesky is in dallas reporter: tonight a multi-state manhunt to find the man police say murdered joshua brown. these suspects are to be considered dangerous because they re armed. reporter: authorities issuing capital murder arrest warrants for thaddeous green and michael mitchell in brown s death. brown, a key witness in the murder trial of ambe