Earlier quoted context omitted.
It's a little harsh to say he deleted the audit trail. He deleted his bash history. Something I do on a near daily basis.
The exact details (which aren't disputed) are covered in: http://online.wsj.com/public/resources/documents/021110aleyn... Basically he'd written a backup program which was specifically designed to compress both his home directory and propriety code from elsewhere on the system into a file (which it would do depended on parameters passed). On his last day of employment he ran it several times with different parameters…
What is way more troubling to me is how apparently easy it is for Goldman to get the highest levels of government involved and throw the criminal book at someone over what is typically a civil matter.