Story highlights Collins said Trump's fight with a Gold Star family was the last straw

But the moderate GOP senator will not be voting for Hillary Clinton, she said

Washington (CNN) Sen. Susan Collins said Tuesday that Donald Trump could make the world "more dangerous" and that his values represent a threat to the Republican Party.

"Donald Trump, in my judgment, would make a perilous world even more dangerous," Collins told CNN's Jamie Gangel. "I worry that his tendency to lash out and his ill-informed comments would cause dangerous events to escalate and possibly spin out of control at a time when our world is beset with conflicts. That is a real problem."

The moderate Republican senator said for her the "tipping point" in opposing Trump came over his feud with the parents of Capt. Humayun Khan, who was killed in the Iraq War. His father, Khizr Khan, harshly criticized Trump at a speech at the Democratic convention and Trump's first reactions were to question why Khan's wife, who was overcome with grief, didn't speak.

"Those are the parents who lost their son in the war in Iraq, when he showed absolutely no empathy or compassion for their terrible loss and instead attacked these two Gold Star parents and also attacked their religion, that was just the final straw for me," Collins said.

The break with Trump was a long time coming for the senator. Collins has spoken out against Trump for a number of his past statements, including when he criticized the service of Arizona Sen. John McCain, who was a POW in Vietnam.

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