London (CNN) -- A man tossed light-blue shaving cream at media magnate Rupert Murdoch during a parliamentary hearing Tuesday.

"You naughty billionaire," the man said, according to the British Press Association, as he hit Murdoch with the foam.

Murdoch appeared stunned but unharmed.

Murdoch's wife, Wendi Deng, who was seated behind him, leaped to her feet and smashed the attacker's hand with her own, pictures from the scene showed.

A police officer arrested the protester, identified by the British Press Association as a man known by the name "Jonnie Marbles" on the social networking service Twitter. CNN wasn't able to independently verify the man's identity.

Police said only that the man was 26 years old, according to the press association.

"It is a far better thing that I do now than I have ever done before," someone using the account posted before the attack, adding the word "splat" as a hashtag, or a term used to categorize and search for posts on Twitter.

Marbles describes himself on the Twitter page as an "activist, comedian, father figure and all-round nonsense." The site links to a blog called "Anarch*ish*, which says Johnny Marbles is not the man's real name.

The incident forced an abrupt recess in the Culture, Media and Sport Committee hearing, called to gather Murdoch's testimony on the phone-hacking scandal involving journalists who worked for the British subsidiary of News Corp., which Murdoch largely controls.

House of Commons Speaker John Bercow was "very concerned" about the incident, according to a spokeswoman.

"It is wholly unacceptable that a member of the public should treat a witness in this way," the spokeswoman said.

CNN's Jonathan Wald contributed to this report.