Venting his fury over the Russia investigation, U.S. President Donald Trump on Sunday asserted that the Obama administration bears some blame for the election meddling, insisted he never denied that the Kremlin interfered in the 2016 U.S. campaign and said "they are laughing their asses off in Moscow."

In a rapid-fire series of tweets from his Palm Beach estate, the president unloaded over the Russia investigation, days after an indictment from special counsel Robert Mueller charged 13 Russians with a plot to interfere in the U.S. presidential election.

While the nearby town of Parkland, Fla., continues to mourn a school shooting that left 17 dead, Russia was clearly top of mind for the president. The administration has focused on the fact that the Russian effort began in 2014, before Trump announced his White House run, and Trump continued that argument Sunday.

He said the top Democrat on the House Intelligence Committee, California Rep. Adam Schiff, "is now blaming the Obama administration for Russian meddling in the 2016 Election."

Trump appeared to be referring to an interview Schiff did with NBC in which the lawmaker said the previous administration should have set up a "more forceful deterrent" against cyberattacks after the 2014 hack of Sony Pictures.

Obama in late 2016 defended his administration's response to the Russian meddling, also saying he had confronted Russian President Vladimir Putin that September, telling him to "cut it out."

It's hard to say that this didn't affect the outcome. It was an exceptionally close election. - Chris Coons, Democratic senator

Trump has not been seen in public since he arrived at his Florida club late Friday, after a visit to the community shattered by the shooting. That evening, he met with first responders, medical personnel and some victims. He skipped his usual stop at his nearby golf course Saturday, but planned to meet with House Speaker Paul Ryan on Sunday at Mar-a-Lago to discuss legislative priorities.

Trump used the Florida shooting to criticize the FBI, saying in a tweet late Saturday that the bureau "missed all of the many signals" sent by the suspect and arguing that agents are "spending too much time trying to prove Russian collusion with the Trump campaign."

"Get back to the basics and make us all proud!" he said.

'Absurd statement'

The FBI received a tip last month that the man now charged in the school shooting had a "desire to kill" and access to guns and could be plotting an attack. But the agency said Friday that agents failed to investigate.

Ohio Gov. John Kasich, a Republican and frequent Trump critic, called that tweet an "absurd statement" on CNN's State of the Union on Sunday.

He said the "FBI apparently made a terrible mistake, and people should be held accountable. But we need leadership out of the executive. This is a great opportunity for common sense steps that can be taken just in the area of background checks."

In his Russia-related posts on Sunday, Trump asserted that he "never said Russia did not meddle in the election" and added: "The Russian 'hoax' was that the Trump campaign colluded with Russia – it never did!"

The president has repeatedly expressed skepticism over Russian election meddling. In November, he said he believed the conclusion of U.S. intelligence agencies that there had been meddling. But Trump also said he believed Putin was sincere when he said Russia didn't interfere.

Trump also argued on Sunday that the ongoing investigations are just what the Russians want, saying: "Investigations and Party hatred, they have succeeded beyond their wildest dreams. They are laughing their asses off in Moscow. Get smart America!"

On Saturday, Trump undercut his national security adviser, H.R. McMaster, after he said evidence of Russian meddling in the 2016 American election is beyond dispute.

Trump tweeted that McMaster left out some details: "General McMaster forgot to say that the results of the 2016 election were not impacted or changed by the Russians and that the only Collusion was between Russia and Crooked H, the DNC and the Dems. Remember the Dirty Dossier, Uranium, Speeches, Emails and the Podesta Company!"

General McMaster forgot to say that the results of the 2016 election were not impacted or changed by the Russians and that the only Collusion was between Russia and Crooked H, the DNC and the Dems. Remember the Dirty Dossier, Uranium, Speeches, Emails and the Podesta Company! —@realDonaldTrump

Trump was continuing his efforts to pin Russian collusion on the Democrats and their nominee Hillary Clinton.

"Crooked Hillary Clinton, lost the 2016 election," Trump tweeted Sunday. "But wasn't I a great candidate?"

'Exceptionally close election'

Speaking on CBS' Face the Nation on Sunday, Democratic Sen. Chris Coons said it wasn't time to draw such conclusions.

"It's hard to say that this didn't affect the outcome. It was an exceptionally close election," Coons said. "I'll remind you one candidate won the popular vote. The other candidate won the electoral vote. But it's not yet clear whether the Russians succeeded in actually changing votes."

Trump also raged against law enforcement over an Obama-era payment to Iran. He tweeted that he's "never gotten over the fact that Obama was able to send $1.7 Billion Dollars in CASH to Iran and nobody in Congress, the FBI or Justice called for an investigation!"

Never gotten over the fact that Obama was able to send $1.7 Billion Dollars in CASH to Iran and nobody in Congress, the FBI or Justice called for an investigation! —@realDonaldTrump

The Obama administration transferred the money to Iran in 2016, using non-U.S. currency. The administration said it was the settlement of a decades-old arbitration claim between the countries. An initial payment was delivered the same day Tehran agreed to release four American prisoners.

The Obama administration eventually acknowledged the cash was used as leverage until the Americans were allowed to leave Iran. Congressional Republicans decried the payment as ransom, which the Obama administration denied.