Robert O'Neill, a former U.S. Navy SEAL, speaks in Maryville, Tennessee, Nov. 6, 2014. Luke Sharrett/Bloomberg via Getty Images

An ex-Navy SEAL who says he killed Osama bin Laden in 2011, was arrested for driving under the influence Friday morning, the Montana Standard in Butte reported.

Rob O'Neill, 39, was found sleeping behind the wheel of a Nissan Sentra parked at a Butte convenience store around 2:30 a.m. MDT, Butte-Silver Bow County Undersheriff George Skuletich told the paper. The engine was running with the tail lights on. Officers who woke him up by opening the car door said he appeared to be impaired. He failed a horizontal gaze test at the scene, and other sobriety tests at the jail.

O'Neill refused a Breathalyzer test. He was released from jail at 4:26 a.m. on a $685 bond. The charge filed Friday by county prosecutors was misdemeanor DUI, a first offense. He was issued a notice to appear at an arraignment by Tuesday.

O’Neill appeared confused, according to the sheriff’s report. He said he had one drink, then denied that. He also said he may have taken Ambien, a prescription sleeping aid. O'Neill told authorities he had flown into Butte from overseas, saying initially from Europe and then Central America.

Sheriff Ed Lester said, "I have great respect for Rob O'Neill and what he has done for our country. That being said, this incident was handled the same way as any other DUI investigation.”

O'Neill told the Washington Post in a 2014 interview that he fired the two shots that killed bin Laden at his compound in Abbottabad, Pakistan. One current and one former SEAL confirmed to the Associated Press that O'Neill was long known to have fired the shots that killed the al Qaeda leader.

He had planned a public 40th birthday party on Saturday and was scheduled to speak at Montana State University on Monday evening, NBC Montana reported.

Just a few weeks ago, in an interview with Fox News, O'Neill warned that there will continue to be terror attacks like those in Brussels and Paris until a coalition of ground troops destroys the Islamic State group “hive” in Raqqa, Syria.

“It seems like they do this every few months,” he said. “It’s going to continue to happen every few months.”

“We’re swatting at the bees, but we need to really take out the hive. And the hive is in Syria. ... We need a plan to get into the Raqqa because that is where the caliphate, the capital of the caliphate, is. We can decide if we want to fight them now or let our grandkids fight them. We’re in a long war.”

O'Neill's claim of credit for killing bin Laden did not please all his comrades, reports noted in 2014. Another SEAL claimed the deed, and both O'Neill and that man, Matt Bissonette, violated non-disclosure agreements they signed as members of the Navy’s most elite special operations force.

In a 2014 interview with CNN, O'Neill said, "But I don't care if I'm 'The Shooter,' and there are people who think I'm not. So whatever."