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1/ Here the steps we took and tools we used for our investigation mapping how the Las Vegas shooting unfolded nytimes.com/2017/10/23/ins…
2/ First, search across social platforms for eyewitness videos of that night. Also use newswires @Storyful and @APVideoHub. We gathered 40.
3/ Include police bodycam video provided by @LVMPD and police and fire scanner audio provided by @Broadcastify
4/ Organize and annotate the footage by location: front, rear and wings of the festival venue, on the streets outside, at the Mandalay Hotel 
5/ Together, the footage conveyed the horror and brutality of the assault from multiple locations. But the chaos it showed needed structure.
6/ Annotated the bursts as I watched. The length, interval, pattern. Awful as they were, they became a scaffolding to build a timeline
7/ Verify burst patterns by lining up the burst audio waveforms. Note the bullet spikes, patterns and pauses in these different videos
8/ Repeat this process and create a complete timeline of the assault using 30+ videos from first bullet to final volley
9/ This proved there were 12 main bursts of fire outward from the hotel, some relentless in frequency, and three intervals of over 1 minute
10/ Verify video locations, e.g. this filmed in taxi at Mandalay Hotel. Clues are street lights by street entrance and distant Luxor Obelisk
11/ This particular video, taken right below the gunman, filmed loud bursts of fire and a dull burst (40 secs in) facebook.com/cori.langdon/v…
12/ Because we had a full timeline, we noticed this as an outlier. No camera filming at the festival during this time picked it up.
13/ This & analysis by @cjchivers @tgneff indicated shots fired inside. Possibly at sec. officer & hotel engineer taking cover in hallway
14/ That scaffolding of a multi-location video timeline gave us a detailed picture of what was happening around the venue between bursts
15/ Moving on: By marking the time displayed in clocks at several points through the footage, we could approximate WHEN the firing began
16/ Some people seeking the story link: nytimes.com/2017/10/23/ins… You may also like these: bit.ly/khan-sheikhoun & bit.ly/turkish-brawl
17/ Back to the start time. Eyewitnesses sent me original videos. Installed phone app to extract EXIF data for video start time: HH:MM:SS
18/ Mark the video times, including @LVMPD vid, on the timeline. Sure, clocks can be off, but 6 of them point to a 3-second starting window
19/ Next, the bullet count. @huang_apiaries showed me how he did this piece with @larrybuch and @adamrpearce. nytimes.com/interactive/20…
20/ I additionally slowed audio to isolate supersonic cracks of bullets from retort of gun chamber (thud) or bullets striking. Example:
21/ Counted & marked rounds using these multiple audio angles of same bursts. @bottidavid, a former Marine working w/ @nytvideo, listened 2
22/ Additional reporting, facts, source information contributed @NYTNational team and visuals from @nytgraphics nytimes.com/interactive/20…
23/ Video expertly edited by @chriscirillo_, motion graphics and editing by Drew Jordan, 3D tour using Google Earth Studio by Nicole Fineman
24/ My sympathies to families, friends who lost loved ones. My respect to officials, bystanders who tried to help. #ends
