DALLAS — President Obama arrived at a memorial service here Tuesday to address another city heartbroken by a mass shooting, seeking to comfort a nation mourning the deaths of five officers while protests over policing have continued in cities across the country. Consoling a nation after a violent episode has become familiar ground for Obama, whose presidency has been marked by tragedies and attacks in places such as a school in Newtown, Conn.; a church in Charleston, S.C; an office holiday party in San Bernardino, Calif.; and many others/Washington Post. More here.