AdvertisementInvestigators struggle to build murder case in death of US Capitol Police officer Brian SicknickHide TranscriptShow Transcriptstrong.AdvertisementInvestigators struggle to build murder case in death of US Capitol Police officer Brian SicknickRelated video above: U.S. Capitol Police officer Brian Sicknick lies in honorInvestigators are struggling to build a federal murder case regarding fallen U.S. Capitol Police officer Brian Sicknick, vexed by a lack of evidence that could prove someone caused his death as he defended the Capitol during last month's insurrection.Authorities...…AdvertisementInvestigators struggle to build murder case in death of US Capitol Police officer Brian SicknickHide TranscriptShow Transcriptstrong.AdvertisementInvestigators struggle to build murder case in death of US Capitol Police officer Brian SicknickRelated video above: U.S. Capitol Police officer Brian Sicknick lies in honorInvestigators are struggling to build a federal murder case regarding fallen U.S. Capitol Police officer Brian Sicknick, vexed by a lack of evidence that could prove someone caused his death as he defended the Capitol during last month's insurrection.Authorities...WW…