The Secret Service is investigating a person who has apologized for hacking into a Hotmail account once used by Mitt Romney.

The hacker, whose identity is unknown publicly, read a Wall Street Journal story about the emails the candidate used to send as governor of Massachusetts from the address mittromney@hotmail.com. The hacker told Gawker that he guessed a security question on the email account about Romney's favorite pet, then used the password to get into Romney's old inbox.

Yesterday the Romney campaign said investigators were working on the case. "The proper authorities are investigating this crime, and we will have no further comment on it," Romney spokeswoman Gail Gitcho said in an email.

The hacker has since apologized in a letter addressed to Romney and published by Gawker. The Romney campaign declined to comment following the hacker's apology.

The person said he or she had deleted the files that were downloaded and changed the password and security question to prevent others from getting into it.

"I engaged in an egregious violation of another persons privacy, a violation made all the worse by way of your being a public figure who has so little privacy to begin with, a figure for whom what privacy can be found is doubtless a valuable gift," the hacker said. "A gift I took away. For this I am sorry. When I hacked in it struck me as funny at first, but now… I have never felt as bad about something I have done as I feel right now."

The Secret Service confirmed to ABC News that it is on the case. "We are investigating and it is an opening investigation," Secret Service spokesman Ed Donovan said.