A former top aide to Pennsylvania's attorney general says his "heart sank a little" when his boss asked him to try to block a special investigation into a grand jury leak.

Bruce Beemer has been testifying against Attorney General Kathleen Kane as she fights perjury and obstruction charges. Investigators say she leaked documents to a newspaper to embarrass a rival.

Beemer said Wednesday he was stunned when he saw the 2014 newspaper article and thought it came from a satellite office. But he came to fear something worse after talking to Kane.

He said Kane asked him to file a court challenge to the outside investigation ordered by the state Supreme Court.

The special prosecutor ultimately charged Kane with leaking the documents and lying to the grand jury. She denies the charges.