VIRGINIA BEACH, Va. — The Virginia Beach employee who shot and killed 12 people at a municipal building gave no hint of the massacre to come when he emailed his resignation letter earlier in the day, saying that he was leaving for “personal reasons” but that “it has been a pleasure to serve.”

The gunman’s two-sentence emailed resignation letter — released by city officials Monday, three days after the shooting — put authorities, the community and victims’ families no closer to understanding why the engineer with 15 years on the job would go on a rampage at work.

Investigators seem stymied. There are no indications the 40-year-old DeWayne Craddock left notes, manifestos, social media posts or any other obvious signs of what motivated him.

Because the email is partially redacted, it’s unclear how long before the shooting it was sent.