It was an ex-IT aide, Jackson Cosko who is the main perp. He was fired and then came up with a scheme for revenge.  He broke into the office and installed keyloggers on the computers.  He got the keys to the office from a friend of his who still worked there.  Here the document from when he pleaded guilty last year. https://cdn.vox-cdn.com/uploads/chorus_asset/file/16011539/usavcosko.pdf