While Jamal Khashoggi's public remarks on the Kingdom of Saudi Arabia were restrained, in private messages he did not hold back, CNN said Monday.

The more than 400 WhatsApp messages between Khashoggi and Montreal-based activist Omar Abdulaziz obtained by the news agency "paint a picture of a man deeply troubled by what he regarded as the petulance of his kingdom's powerful young prince."

Khashoggi, a Saudi journalist and columnist for The Washington Post, went missing after entering the Saudi Consulate in Istanbul on Oct. 2.

After initially saying he had left the consulate alive, weeks later the Saudi administration admitted he was killed there.

"The more victims he eats, the more he wants," Khashoggi said in a message sent in May. "I will not be surprised if the oppression will reach even those who are cheering him on.

"He loves force, oppression and needs to show them off...but tyranny has no logic," Khashoggi added, referring to bin Salman.

The messages revealed a plan between the two for an online youth movement, consisting of an "electronic army" to engage Saudi youth and debunk state propaganda on social media, in an attempt to hold Saudi Arabia to account.

The movement was called "cyber bees,” a name that came from earlier efforts to create a hub for documenting rights abuses in the country.

In August, however, Abdelaziz noted he had reason to believe the Saudi government found out about the initiative.

Bill Marczak, a research fellow at Citizen Lab, said there is high confidence Abdulaziz's phone was hacked by a Saudi-linked operator of NSO Group’s Pegasus, an Israeli-made spyware.

"The hacking of my phone played a major role in what happened to Jamal, I am really sorry to say," Abdelaziz told CNN. "The guilt is killing me."

Abdulaziz's legal team filed a lawsuit in Israel on Sunday, arguing NSO broke international laws by selling its software to Saudi Arabia, knowing it could be used to violate human rights.

Last May, Abdulaziz said he met two Saudi government officials in Montreal, and recorded their conversations, sharing them with CNN.

The officials said they were sent by bin Salman, who wanted to offer him a job.

Abdulaziz consulted with Khashoggi after the officials told him to go to the Saudi embassy to fill out paperwork, and Khashoggi told him to not go and to only meet in public places.

"On October 2, Khashoggi did the opposite. It was the last time he checked his WhatsApp messages," CNN said.