Transcript for Timeline of Dayton shooting becomes clearer with new images, video
And we begin with new surveillance, and what it reveals about the gunman in Dayton. You see him arriving in the bar, and walking after going to his car and changing his clothes, then carrying a heavy backpack. Ducks into an alley and puts on body armor. Not long after, the shooting began. And 26 people shot in just 32 seconds. Among the dead, his own sister. And Eva pilgrim is leading us off. Reporter: Tonight, nine days after a gunman killed nine people in downtown Dayton, officials using never before seen surveillance images and video piecing together the most detailed timeline yet of Connor BETTs' deadly rampage. Authorities say Connor BETTs got to the area aound 11:00 the night of the shooting. You see in this surveillance video him arriving with his sibling and a friend. The three going to blind Bob's bar. Then at 12:13, BETTs leaves his sister and friend at blind Bob's, and goes to Ned peppers across the street. He's there for 30 minutes before going back to his car, where cameras capture him changing. He stood for nine minutes behind the bars before he's sn on video again. This time, body armor on, gun in hand, walking down an alley. Just after 1:00 A.M., the terror began. We believe that the shooting started at approximately 1:05 and 35 seconds. We believe it ended at 1:06 and 7 seconds, that's 32 seconds. Reporter: Police quick, responding to the scene in 15 seconds, taking him down in the doorway to Ned peppers. The aftermath, more than a dozen taken the hospital. Nine people were killed, including the shooter's own sister. Tonight investigators revealing BETTs was in contact with his sister throughout the night. Even calling her at one point. As to whether or not he shot her deliberately? Some are saying absolutely not, he was not intentional. Some say, no, it had to be. I would say it's inconclusive. And Eva is back with us tonight. And police revealing he had been there the night before. But they still haven't revealed a motive? That's right. They think BETTs planned the shooting, and they think he acted alone. Saying he was in the area the night before the shooting. They're trying to figure out how long he had been planning this attack. Eva, thank you.
This transcript has been automatically generated and may not be 100% accurate.