Shooter

Archive of Google Search Dec 5, 2016 - 04:25:41 UTC
https://archive.is/KHiJT

D.C. Police detain suspect with a weapon at Comet Ping Pong restaurant 
https://web.archive.org/web/20161204212228/https://www.washingtonpost.com/news/local/wp/2016/12/04/d-c-police-respond-to-report-of-a-man-with-a-gun-at-comet-ping-pong-restaurant/

UTC to EST (Washington D.C.) -5h, which means that the archived Google Search was taken at Dec 4,2016 - 23:25:41
The search shows articles which report the incident up to 20 hours before police was informed at 3pm.

Additionally the Original Article was written Dec 4th, as you can see in the archived version and the URL.
The article now shows the following:

https://www.washingtonpost.com/news/local/wp/2016/12/04/d-c-police-respond-to-report-of-a-man-with-a-gun-at-comet-ping-pong-restaurant/

Just one example why you should take media reporting with a grain of salt.

D.C. police around 3pm

https://archive.fo/JlfiX