didn t testify. but former national security adviser john bolton could know more than all of them about the allegations that president trump abused his power to leverage the ukrainians to investigate joe and hunter biden. john bolton has been one of the most mysterious figures in the whole ukraine saga. one of the biggest stars players in this episode with ukraine yet an offstage character almost the entire time in the impeachment probe. reporter: friday after more than two months of silence a tease from john bolton. in a series of tweets and later in an encounter with reporters he accused the white house of blocking his access to his personal twitter account. they attached software to it. ant tw and twitter unattached it. reporter: bolton didn t explain what it meant and the white house denied freezing the twitter account. of course not. no. i actually had a good relationship. reporter: in a tweet bolton asked whether the white house