Donald Trump just might get a visit from the same Secret Service that is charged with protecting him.

On Tuesday, he seemed to casually suggest that, if his supporters aren't able to stop Hillary Clinton from becoming president via the ballot box, then perhaps they could just shoot her.

The Republican presidential nominee was stoking fears that Clinton will abolish the Second Amendment if she wins the presidency, and alluded that she would try to do this by nominating Supreme Court justices in favor of doing so.

"If she gets to pick her judges, nothing you can do folks," he said. "Although the Second Amendment people maybe there is, I don't know."

Trump on Clinton picking judges: "Nothing you can do, folks. Although, the 2nd Amendment people, maybe there is" pic.twitter.com/uvoRDBbwMH — Mashable News (@MashableNews) August 9, 2016

That flippant comment alarmed a lot of people on Twitter. Rep. Eric Swalwell (D-Calif.) called for the Secret Service to investigate immediately what he called a threat on Clinton's life. A spokesperson for the Secret Service told Mashable "we are aware of the [Trump] comment."

Donald Trump suggested someone kill Sec. Clinton. We must take people at their word. @SecretService must investigate #TrumpThreat. — Rep. Eric Swalwell (@RepSwalwell) August 9, 2016

Claiming the election will be rigged, "jokingly" encouraging supporters to assassinate political opponents—Trump is undermining democracy. — Dana Schwartz (@DanaSchwartzzz) August 9, 2016

Look, it's not like this Trump line is out of nowhere. He praised adviser who called for executing HRC just days ago https://t.co/NBBGKmgW2S — Benjy Sarlin (@BenjySarlin) August 9, 2016

If Trump's comment is a joke, can someone explain what is funny about it? — Jeet Heer (@HeerJeet) August 9, 2016

If Trump wants to be the "law and order candidate," he might want to brush up on this part of the US Code: pic.twitter.com/aXpyVQXrX6 — Kevin M. Kruse (@KevinMKruse) August 9, 2016

There is never a New And Improved Trump. There is always a Briefly Scripted Trump, eternally followed by a deeper descent into darkness. — Daniel Dale (@ddale8) August 9, 2016

And at least one person at the rally seemed to think Trump may have gone too far.

Guy behind Trump immediately realized what he said was a problem. https://t.co/F3mSP9GLqt — Chris Vannini (@ChrisVannini) August 9, 2016

The Clinton campaign responded to the incident, calling Trump "dangerous."

"A person seeking to be the President of the United States should not suggest violence in any way." pic.twitter.com/Uu55CBCqdK — Hillary Clinton (@HillaryClinton) August 9, 2016

JUST IN: Statement from Clinton campaign manager Robby Mook responding to Trump's "second amendment" line pic.twitter.com/aYfuETchgp — Gabriel Debenedetti (@gdebenedetti) August 9, 2016

The Trump campaign said the candidate was simply talking about "unification."

Trump campaign releases statement on his 2nd amendment remarks: pic.twitter.com/0rrFt6XnI4 — Nick Corasaniti (@NYTnickc) August 9, 2016

And it's entirely possible he was, or was perhaps suggesting armed rebellion rather than assassination.

The problem is that Trump rambles so much that what could have been a banal rah-rah point sounded like a call for assassination. — daveweigel (@daveweigel) August 9, 2016

From context, it's also possible that Trump was floating idea of armed rebellion against bad SCOTUS decisions, not assassination. — Philip Klein (@philipaklein) August 9, 2016

Of course...

"You're aren't just responsible for what you say. You're responsible for what people hear."

- Michael Hayden on CNN just now. — Katy Tur (@KatyTurNBC) August 9, 2016

Trump has also recently suggested that the presidential election might be "rigged," which many have said is an attempt to undermine the United States' basic democratic principles.

Update: Aug. 9 4:39 p.m. PT

Gabrielle Giffords, a former Democratic member of the House of Representatives who resigned in 2012 after surviving an assassination attempt, has responded to Trump's remarks.

.@realDonaldTrump might astound Americans on a routine basis, but we must draw a line between political speech & suggestions of violence. — Gabrielle Giffords (@GabbyGiffords) August 9, 2016

When candidates descend into insult, our politics follow suit. When they affirm violence, we should fear that violence will follow. — Gabrielle Giffords (@GabbyGiffords) August 9, 2016