 -- Over the weekend, President Donald Trump suggested that the FBI’s Russia investigation had caused the agency to divert resources or attention that could have prevented last week’s school shooting in Parkland, Fla.

“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 tweeted Saturday.

His message came just one day after special counsel Robert Mueller charged 13 Russians for their alleged roles in a complex operation to sway the 2016 presidential election.

Federal law enforcement officials say Trump’s posting misstates how the FBI actually works.

The FBI has a broad mandate and spends every day focusing on multiple threats at once – terrorists, bank robbers, child predators, cyber criminals, corrupt politicians, gun traffickers, foreign spies, and many more.

There are about 35,000 people working for the FBI, including about 12,000 agents, according to FBI statistics.

The FBI has “a lot of people,” one federal law enforcement official told ABC News. “They’re not all working on Russia, I can tell you that. There’s a lot of other stuff going on.”

On Wednesday, 19-year-old Nikolas Cruz opened fire inside Stoneman Douglas High School in Parkland, Fla., killing 17 people and injuring many others. Two days later, the FBI acknowledged that last month, “a person close to Nicolas Cruz” contacted an FBI tip line “to report concerns about him,” but “protocols were not followed” and the information was never passed on to authorities in Florida.

When the FBI receives a call like that from the public, the call goes to a center in West Virginia run by the FBI's Criminal Justice Information Services Division. The call center is supposed to assess the information, and if it is deemed a potential threat the information should be sent to the appropriate FBI field office. In the Cruz case, the information should have been deemed a potential threat to life and should have been sent to the Miami field office for further investigation, but the information was never deemed a threat to begin with, so it was never passed on, the federal law enforcement official said.

Nevertheless, personnel at the FBI’s call center would “absolutely not” ever be working on the Russia case, the official said.