Mark Zuckerberg toted samurai sword around Facebook office, mock

Paul Sakuma/AP

He played Samurai CEO.

Baby-faced exec Mark Zuckerberg once stalked Facebook's offices clutching a samurai sword and threatened to chop off the heads of any of his minions who produced subpar work, a new book reveals.

Noah Kagan, who was employee No. 30 at Facebook, has written an e-book describing his eight-month stint as a product manager at the then-startup in 2005, Business Insider reports.

In the memoir, the Berkeley grad recalled the 23-year-old Zuckerberg's 'immature' management style, which included mock-threatening employees with the giant blade.

'Where the hell he got that samurai sword, who the hell knows? Luckily, no employees were harmed while I was there,' Kagan writes, according to Business Insider.

'He'd come around and pretend to cut you joking if you take down the site he'll chop your head off,' Kagan says.

'You have to remember you have a 23-year old uber nerd running one of the fastest-growing sites on the Web.'

Elsewhere, Kagan recalls Zuckerberg dumping water on an engineer's computer after he and Kagan spent a month on a project 'we thought Mark would love.'

'Mark thought it was s--t,' Kagan writes.

'I know so because instead of giving product feedback, he screamed 'This is s--t - redo it!,' threw water on Chris' computer, and walked away. All of us stood around in shock.'

After Facebook canned him, Kagan, 32, worked for personal finance service Mint and now runs AppSumo, a deals website for online services.