The Democrat tells a rally there could be "tremendous consequences" from her Republican rival's comments.
Mrs Clinton said Mr Trump lacks the temperament to be commander-in-chief
White
House candidate Hillary Clinton has accused Donald Trump of "casual
inciting of violence" after his remark about gun rights.
At a rally in Des Moines, Iowa, Mrs Clinton said Mr Trump had "crossed the line" by saying there may be something gun rights supporters "can do" to stop her.
Critics said the Republican presidential candidate had advocated that his Democratic rival or her Supreme Court nominees could be shot.
Mrs Clinton, who is leading the race for the 8 November election, told supporters Mr Trump's remark showed he lacks the temperament to be commander-in-chief.
Mrs Clinton said that words matter and "if you are running to be president or you are president of the United States words can have tremendous consequences
Video:
Donald Trump's 'Assassination Threat' Against Hillary Clinton
The US Secret Service has reportedly spoken to the Trump campaign about his remarks."Hillary wants to essentially abolish the Second Amendment," Mr Trump told a rally in Wilmington, North Carolina, on Tuesday.
He was referring to the US Constitution's clause that enshrines "the right to bear arms".
"If she gets to pick her judges, nothing you can do, folks," he added.
"Although the Second Amendment people - maybe there is, I don't know," he said
Video:
Trump Accused Of Gun Threat Against Clinton
Mr Trump later maintained he never advocated violence and his words were twisted for political purposes."Give me a break," Mr Trump said afterwards, insisting he was referring to the power that voters hold.
He told Fox News that "there can be no other interpretation".
But the Clinton campaign decried Mr Trump's "dangerous" language.
Her camp began emailing supporters for $1 donations to "show that we don't tolerate this kind of politics in America".
The firestorm will do little to allay Republican leaders' concerns about Mr Trump's inflammatory remarks.
Many conservatives fear the tycoon's outbursts could damage not only his White House prospects, but the re-election hopes of many in the party.
Mrs Clinton was herself condemned during the 2008 Democratic primary race when she appeared to suggest Barack Obama could be assassinated.