President Donald Trump took his battle with the FBI to a new level late Saturday night, when he tweeted that the bureau was too caught up in the Russia probe and failed to see the signals leading to Wednesday’s shooting massacre at a south Florida high school.

“Very sad that the FBI missed all of the many signals sent out by the Florida school shooter. This is not acceptable,” the president tweeted. “They are spending too much time trying to prove Russian collusion with the Trump campaign – there is no collusion.”

Trump was referring to the FBI’s admission earlier this week that it failed to investigate a Jan. 5 tip that warned that Nikolas Cruz, the 19-year-old man who is accused of killing 17 people at Marjory Stoneman Douglas High School in Parkland, Fla., posed a deadly threat.

The information was not passed to the bureau’s Miami field office. Attorney General Jeff Sessions has ordered a review of the FBI’s handling of the matter. Florida Gov. Rick Scott called on FBI DIrector Christopher Wray, a Trump appointee, to resign.

For his part, Wray said earlier this week: “We have spoken with victims and families, and deeply regret the additional pain this causes all those affected by this horrific tragedy.”

The FBI has 35,000 employees, including special agents and various other staffers. A representative of the bureau was not immediately available for comment.

Trump has routinely targeted the FBI for criticism as a probe into potential collusion between Trump’s presidential campaign and the Kremlin has cast a shadow over his presidency.

In May, he fired then-FBI Director James Comey, and then told NBC’s Lester Holt that he had been thinking about the Russia probe when he decided to sack him. In January, Deputy FBI Director Andrew McCabe, whom Trump often accused of political bias, retired from the agency. McCabe also led the FBI on an interim basis before Wray was confirmed to replace Comey.

The president’s tweet Saturday night follows a slew of federal grand jury indictments Friday that stem from special counsel Robert Mueller’s Russia probe. Deputy Attorney General Rod Rosenstein appointed Mueller to take over the probe last year after Trump fired Comey. Trump has repeatedly denied collusion and has called the investigation a “witch hunt” and a “hoax.”

Trump changed his tune somewhat Friday, acknowledging Russian efforts to interfere in U.S. affairs while claiming that the indictments had vindicated him.

“Russia started their anti-US campaign in 2014, long before I announced that I would run for President,” Trump tweeted late Friday evening. “The results of the election were not impacted. The Trump campaign did nothing wrong – no collusion!”

In a press conference Friday, Rosenstein said this particular indictment didn’t have any allegation of American involvement or impact on the election. The special counsel accused 13 Russian nationals and three Russian entities of meddling in the 2016 election, with the intention of sowing chaos and aiding Trump’s push for the White House.