Despite what others are saying about why he was not charged with these crimes, the real reason is because he is being indicted with these crimes, federally, in Maryland on those charges. He will face that trial next.

Now, to be fair, these allegations (not lies, allegations) could be just that. Allegations. The prosecution will need to prove them to get a conviction. The reason he is facing these separately could be that these attempted murder of a federal witness charges are much harder to prove and thus convict on.