When U.S. Sen. Dan Sullivan walked onstage at Bartlett High School on Saturday, the packed auditorium of about 600 people applauded, whistled and booed.

"OK, I can't tell if those are boos," Sullivan, Alaska's Republican junior senator, said into the microphone.

"Don't answer, you don't have to answer that," he said, as a few in the crowd interjected: "Those are boos!"

Saturday marked Sullivan's first town hall meeting in Anchorage since the inauguration of President Donald Trump. Across the country, some town hall meetings hosted by members of Congress have devolved into hostile, one-way shouting matches in the aftermath of the election.

In Anchorage, the 90-minute meeting included about a 20-minute update from Sullivan about policy issues, followed by more than an hour of questions from the audience, many about concerns with the Republican effort to repeal and replace the Affordable Care Act.

A couple of times, the crowd erupted into a chant of "single payer, single payer," advocating for a system in which health insurance is provided by one entity, such as the federal government.

Sullivan told the crowd he supported the "repeal and repair" of the ACA, and thought it appropriate for health insurance to cover pre-existing conditions. He said he was focused on structural issues in Alaska's health care system and how to decrease high costs in the state.

"The Affordable Care Act was a one-size-fits-all approach to health care," he said. "It certainly hasn't worked for Alaska."

Sullivan said he did not support a single-payer system, and a majority of people in the audience held up red pieces of paper to signify their disagreement. Boos filled the auditorium.

The red papers and boos re-emerged often, including when Sullivan mentioned Trump, Education Secretary Betsy DeVos and new U.S. Supreme Court Justice Neil Gorsuch, and when Sullivan said he supported the federal government rolling back "onerous regulations on the economy."

Some in the crowd also shouted interjections as Sullivan spoke. When the senator talked about the national debt, some yelled to tax the corporations. When Sullivan said he did not support putting drug addicts in jail, people yelled that he voted to confirm Jeff Sessions as attorney general.

When Sullivan said he wouldn't support or defend Trump's behavior if he disagreed with it, people shouted: "so racism," "sexual assault," "corruption."

In a couple of instances during the meeting, Sullivan told the audience to be respectful.

"Don't be the first group that doesn't show respect," he said. He later repeated: "You don't want to be the only town hall in Alaska where you're being rude to your fellow Alaskans by interrupting, so let's keep this civil."

While there was a lot of red paper and boos Saturday, the crowd also had green papers to show their support.

Many people held up the green sheets when Sullivan talked about a bill to provide more resources for victims of domestic violence; how he supported investigating possible coordination between Russia and the Trump presidential campaign, and when he said "we're clearly seeing the effects of climate change in Alaska."

"That's the most green I've gotten all night," Sullivan said after his climate change remark.

During the meeting, two people in the crowd held up Trump-Pence campaign signs, and one person spoke out against the ACA and his own expensive health care premiums. Sullivan told the man he spoke for "hundreds and hundreds of Alaskans."

"No," some in the crowd cried out.

Many in the crowd grew disgruntled over Sullivan's responses to other queries — shouting that he wasn't answering the question and chanting: "Yes or no! Yes or no!"

That's the response Sullivan got after a question about whether he supported Medicaid expansion and if he would support funding Planned Parenthood.

Sullivan said he wanted to make sure the people who received health care coverage under Medicaid expansion "do not have the rug pulled out from under them."

About Planned Parenthood, he said, "I actually think it would be much more fair and effective if we took the $500 million that Planned Parenthood gets every year and distribute that to community health clinics."

The town hall meeting went from 4:30 to about 6:15 p.m. At the meeting's end, Dan Boccia, 48, sat outside the school where some other crowd members had gathered.

Boccia, who did not vote for Sullivan in 2014, said he left the meeting with "mild disappointment" in both the crowd's behavior and Sullivan's answers.

"I thought the crowd was rude a lot of times. I didn't appreciate just the yelling in the middle of the assembly," he said. "I thought Sullivan in some cases had difficulty directly answering the questions. I felt like there was a little bit of deflection."