Journalist Glenn Greenwald on Monday said the United Kingdom’s nine-hour detention of his partner was “a failed attempt at intimidation” that has hardened his resolve to reveal more secrets about state-sponsored surveillance.

“[I’m going] to write much more aggressively than before,” the reporter told reporters in Rio de Janeiro, according to The Associated Press. “I have many documents about the system of espionage of England, and now my focus will be there, too. I think they’ll regret what they’ve done.”

David Miranda, Greenwald’s partner, who lives with him in Rio de Janeiro, was detained in Heathrow Airport for nine hours Sunday by London police, who used their authority under the U.K.’s Terrorism Act to detain individuals for long periods without making an arrest.

Miranda was in London on business for The Guardian, the newspaper Greenwald’s writes for and the recipient of many documents leaked by Edward Snowden that detail domestic surveillance practices in several agencies, including the U.K.’s own Government Communications Headquarters.

Greenwald took issue Monday with news headlines that he believes suggested he had become vengeful following his partner’s interrogation, saying that, while he had become emboldened, he was not pursuing a vendetta.

Greenwald claimed via Twitter that, when asked about the consequences of the U.K.’s detention of Miranda, he said “When they do things like this, they show the world their real character. It’ll backfire. I think they’ll come to regret it.”

He said a Reuters report had distorted the quote into an open threat that the U.K. government would be “sorry” for detaining Miranda.