WhatsApp CEO Jan Koum has issued a public apology for "irrational" behavior that resulted in an ex-girlfriend taking out a restraining order against him almost 20 years ago.

"I feel I was irrational and behaved badly after we broke up," Koum said in a statement today. "I am ashamed of the way I acted, and ashamed that my behavior forced her to take legal action. I am deeply sorry for what I did."

Granted in February 1996, the restraining order came after the ex-girlfriend filed a civil harassment claim, detailing multiple incidents to the San Jose, Calif., state court that included verbal and physical threats from Koum. According to the documents, the woman had to change her school records and was prevented from attending college classes because of the incidents.

"Over the years, I have thought a lot about that difficult period of my life," said the WhatsApp founder, as quoted by Bloomberg News. "I have many regrets and things I wish I could go back and change, but I have also worked hard and tried to improve myself."

Facebook acquired WhatsApp in a $19 billion deal in February, marking the biggest startup purchase in history. The messaging app, which has passed half a billion users, is purportedly still its own company, and Koum has vowed that user data will remain private.

In response to the restraining order report, a Facebook spokesman said, "Jan has written a thoughtful and honest response that we believe demonstrates the sincerity of his remorse over what happened nearly two decades ago," according to Bloomberg.

The social network's purchase of WhatsApp made users somewhat uneasy and inspired the Federal Trade Commission to issue a stern warning to the social network. In the past, Koum has stated that messages are deleted after they go through the systems, leaving no data to be mined.

Earlier this month, the European Union finally cleared Facebook's purchase of WhatsApp after an antitrust inquiry, TechCrunch reported.

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