Story highlights Congresswoman calls for Trump's removal from office through the 25th Amendment

Democrat Jackie Speier is "concerned about him having his finger on the button that could send nuclear warheads around the world."

(CNN) Democratic Rep. Jackie Speier is voicing concerns over President Trump's mental fitness and calling for him to be removed from office through the 25th Amendment.

In comments Tuesday on CNN, Speier said there's "a growing mountain of evidence that the president has been very erratic" and "has shown a mental instability."

"It was crystallized last week with a combination of his comments about fire and fury that he offered up against Kim Jong-un and North Korea and how we would take him out, followed by his back and forth on Charlottesville and how he really became almost abusive in calling people out when he was really telling from his soul what he thought about the Charlottesville incident," she told CNN's Jim Sciutto.

"If you go back in time, like six years, and watch interviews that he gave then where he could put a whole sentence together, but now tends to put a few words together and then goes off into another sentence unrelated to the first," she added. "It is an indication to me that there is some trouble there that is more than just a one-off."

POTUS is showing signs of erratic behavior and mental instability that place the country in grave danger. Time to invoke the 25th Amendment. — Jackie Speier (@RepSpeier) August 16, 2017

Speier, who serves on the Armed Services and Intelligence Committees, said she is genuinely worried for the American people.