 -- White House press secretary Sarah Sanders has walked back President Donald Trump's tweet from last weekend suggesting the FBI could have prevented the Parkland high school shooting if it hadn't been so focused on the Russia investigation.

On Friday, the FBI said it failed to follow up on a tip about the Parkland shooter. And Tuesday, when asked if Trump believes the FBI missed warning signs because of the time it's spending on the Russia investigation, Sanders said that was "not necessarily" the cause.

"I think he was speaking - not necessarily that that is the cause. I think we all have to be aware that the cause of this is that of a deranged individual that made a decision to take the lives of 17 other people. That is the responsibility of the shooter certainly not the responsibility of anybody else," Sanders said.

Sanders tried to clarify when asked if the tweet Trump sent late Saturday night from his private Mar-a-Lago estate in Florida was a "mistweet."

"I think he's making the point that we would like our FBI agencies to not be focused on something that is clearly a hoax in terms getting the Trump campaign and its involvement," Sanders said.

Trump's tweet outraged some survivors of the school shooting that killed 17 last week.

Over the weekend, Trump fumed about Friday's indictment from the special counsel's investigation that accused 13 Russians of interfering in the 2016 election. Trump pointed at the Obama administration for not intervening earlier. "The 'Russian hoax' was that the Trump campaign colluded with Russia - it never did!" he tweeted.

Sanders, asked Tuesday if the president believes Russia meddled in the election, gave the strongest acknowledgement yet from the White House.

"Absolutely," said Sanders. "It's very clear that Russia meddled in the election. It's also very clear that it didn't have an impact on the election. And it's also very clear that the Trump campaign didn't collude with the Russians in any way for this process to take place."

Sanders also defended the administration's response to that Russian interference.

"President Trump and the administration have made it clear that interference in our elections will have consequences and we're going to continue to impose consequences in response to Russian cyber attacks. Just last week, we called out Russia by name. It was one of the first times that you've seen something like that take place. We're going to continue doing things like that," Sanders said.

Asked why Trump hasn't condemned Russia, Sanders said, "He has been tougher on Russia in the first year than Obama was in eight years combined. He's imposed sanctions; he's taken away properties; he's rebuilt our military. He has done a number of things to put pressure on Russia and to be tough on Russia."

Sanders cryptically made reference to a new, unreported incident in which Trump came down on Russia.

"Last week, there was an incident that will be reported in the coming days in another way that this president was tough on Russia," said Sanders.

The White House has not revealed any details about that incident.