http://www.sfgate.com/ndnvideos/?ndn.trackingGroup=45981&ndn.siteSection=sfgate&ndn.videoId=31401957&freewheel=45981&sitesection=sfgate&vid=31401957
Videos posted on social media showed one of the officers apparently punching a handcuffed Michael Smith, 22, whom police had detained in response to reports of an armed man trying to rob someone on a BART train.