A group of veterans will ask Sen. John McCain and other Republican leaders on Thursday to un-endorse Donald Trump following his criticism of a Gold Star family.

Perry O’Brien, a veteran of Operation Enduring Freedom in Afghanistan, will lead the group to deliver a petition with more than 50,000 signatures to the offices of congressional Republicans asking them to withdraw their support for the GOP nominee over his “unrelenting attack” on the family of Capt. Humayun Khan, a Muslim soldier who was killed in Iraq.