"Very sad that the FBI missed all of the many signals sent out by the Florida school shooter. This is not acceptable. They are spending too much time trying to prove Russian collusion with the Trump campaign — there is no collusion. Get back to the basics and make us all proud!" Trump posted on Twitter.
Nicholas Cruz, a 19-year-old former high school student, has been charged with killing 17 people in a rampage with an AR-15 semi-automatic rifle at Stoneman Douglas High School on Wednesday.
The US Congress is currently investigating Russia's alleged meddling in the 2016 US election and collusion between Trump's campaign team and the Kremlin. Another investigation into the purported interference is being conducted by the FBI and the Department of Justice under Special Counsel Robert Mueller.
The Trump administration and senior Russian officials have repeatedly refuted the allegations of collusion.