The two major party candidates' responses again highlighted the sharp differences in their foreign policy stances, with Trump reiterating his belief that the USA needs to be "tough" in its response to terrorism.
On Thursday night, a man driving a truck plowed through a large crowd of people celebrating France's Bastille Day in Nice, killing at 84 people and wounding many others.
The former reality TV star said "it's about time" Barack Obama to recognised the problem was "radical Islam". "We have a president that doesn't want to call it what it is", he said.
"I would, I would". This is war, "Trump answered".
"If you look at it, this is war coming all different parts".
Clinton also dismissed Trump's criticism of the administration's decision to allow 10,000 Syrian refugees to enter the USA because of the potential of terrorists entering the country by posing as refugees. "Who knows? Maybe you will be surprised and maybe we will all be surprised", he said. "We should frankly test every person here who is of a Muslim background, and if they believe in Sharia, they should be deported", Gingrich said. But, she argued, greater intelligence gathering, not military force, was necessary.
Clinton released a longer press statement, expressing similar remorse, and pledging the attacks would only strengthen the resolve of the United States' Western allies to defeat terrorism.
GETTY SCENE Armed officials cordon off the area of the attack
"One of my priorities is to launch an intelligence surge. I would be very focused on working with our partners and allies and intensify our efforts against the ideologues that pedal radical jihadism online".
"This is a war against these terrorist groups, these radical jihadist groups", she added. "I would be so extreme in terms of documentation", Trump said.
"Another awful attack, this time in Nice, France".
After the terror attack in Orlando one month ago, US authorities had already been on high alert ahead of next week's Republican National Convention, says Ron Hosko, CBS News Security Consultant.
Republican Donald Trump canceled a planned press conference to unveil his vice presidential running mate Thursday night as the full scope of the horrific attack was becoming clear. Both presidential candidates said we are in a war with ISIS but offered different ways to fight back.
Other notable political figures stood in solidarity with those affected by the attack.