(Vancouver, WA)  --  Authorities say a murder suspect has died two days after being found unresponsive in his cell at the Clark County Jail.  Officials say David Barker, who was accused of the May 2015 murder of Sharon Allison of Vancouver, likely committed suicide.  Barker was arrested in March and was awaiting trial for the murder.  There's no word yet on the manner of Barker's death.