NYT:

The police arrested three people, but there was some uncertainty about the number of gunmen. At first, officials said that multiple snipers had carried out a coordinated ambush of the officers — some of whom were shot in the back, the chief said — but later, Homeland Security Secretary Jeh Johnson said that the suspect killed by the police, identified as Micah Johnson, 25, appeared to be the sole gunman and to have no links with any international terrorist organizations... Chief Brown declined to identify the people who were arrested, or to say if there might have been others involved. The gunman claimed he acted alone, he said, but “we’re not satisfied that we’ve exhausted every lead.”

As if we needed to be reminded after Orlando, Sandy Hook, Aurora: One deranged asshole armed with a powerful gun can do a whole lot of damage.