"It was a targeted attack," said Kellermann, who serves on the International Cyber Security Protection Alliance.

Early on Wednesday, Mr. Kellermann went to the basement of his brick home and hanged himself, according to people familiar with the situation who were not authorized to speak.

The pressures were already immense when David B. Kellermann was promoted to the top financial position at the mortgage giant Freddie Mac last September. Then they got even worse.