A white, 17-year-old police admirer was arrested Wednesday after two people were shot to death during a third straight night of protests in Kenosha over the police shooting of a Black man, Jacob Blake. Kyle Rittenhouse, of Antioch, Illinois, was taken into custody in Illinois on suspicion of first-degree intentional homicide. Antioch is about 15 miles from Kenosha. Two people were killed Tuesday night and a third was wounded in an attack apparently carried out by a young white man who was caught on cellphone video opening fire in the middle of the street with a semi-automatic rifle. “I just killed somebody,” the gunman could be heard saying at one point during the rampage that erupted just before midnight.

In the wake of the killings, Wisconsin Gov. Tony Evers authorized the sending of 500 members of the National Guard to Kenosha, doubling the number of troops. The governor’s office said he is working with other states to bring in additional National Guard members and law officers. Authorities also announced a 7 p.m. curfew, an hour earlier than the night before. “A senseless tragedy like this cannot happen again,” the governor, a Democrat, said in a statement. “I again ask those who choose to exercise their First Amendment rights please do so peacefully and safely, as so many did last night. I also ask the individuals who are not there to exercise those rights to please stay home and let local first responders, law enforcement and members of the Wisconsin National Guard do their jobs.”

In Washington, the Justice Department said it is sending in the FBI and federal marshals in response to the unrest. The White House said up to 2,000 National Guard troops would be made available.

The dead were identified only as a 26-year-old Silver Lake, Wisconsin, resident and a 36-year-old from Kenosha. The wounded person, a 36-year-old from West Allis, Wisconsin, was expected to survive, police said. “We were all chanting ‘Black lives matter’ at the gas station and then we heard, boom, boom, and I told my friend, `‘That’s not fireworks,’” 19-year-old protester Devin Scott told the Chicago Tribune. “And then this guy with this huge gun runs by us in the middle of the street and people are yelling, ‘He shot someone! He shot someone!’ And everyone is trying to fight the guy, chasing him and then he started shooting again.”

U.S. health officials have sparked criticism and confusion after posting guidelines on coronavirus testing from the White House task force that run counter to what scientists say is necessary to control the pandemic. The new guidance says it is not necessary for people who don’t feel sick but have been in close contact with infected people to get tested. It was posted earlier this week on the website of the Centers for Disease Control and Prevention.

The CDC previously had advised local health departments to test people who have been within 6 feet of an infected person for more than 15 minutes. But on Monday a CDC testing overview page was changed to say that testing is no longer recommended for symptom-less people who were in close contact situations. There was a caveat, however. Testing may be recommended for those with health problems that make them more likely to suffer severe illness from an infection, or if their doctor or local state officials advise they get tested. CDC officials referred all questions to the agency’s parent organization, the U.S. Department of Health and Human Services in Washington, D.C. That suggests that HHS ordered the change, not CDC, said Jennifer Nuzzo, a Johns Hopkins University public health researcher.

After Twitter lit up with head-scratching and alarm about the change, HHS officials sent an email Wednesday saying the guidance was revised “to reflect current evidence and the best public health interventions,” but did not detail what the new evidence was. The officials also said they wanted to emphasize that people should follow measures designed to help stop spread of the virus, like wearing a mask, staying at least 6 feet apart from others and washing hands. The decision came out of meetings of a White House coronavirus task force, HHS officials said.

In a call with reporters later Wednesday, Dr. Brett Giroir, the HHS assistant secretary for health, said the guidance language came from the CDC. But he also said many people were involved in “lots of editing, lots of input.” He said federal officials achieved consensus but it was difficult to attribute the final language to any one source. “Its kind of hard to know how much was written by what person,” Giroir said.

Across the country, public health experts called the change bizarre. They noted that testing contacts of infected people is a core element of public health efforts to keep outbreaks in check, and that a large percentage of infected people — the CDC has said as many as 40% — exhibit no symptoms. “I was taken aback and didn’t know that it was under consideration,” said John Auerbach, president of Trust for America’s Health, a nonprofit that works to improve U.S. preparedness against disease. “The recommendation not to test asymptomatic people who likely have been exposed is not in accord with the science.”

Ultimately, restricting testing could be self-defeating, because it could skew the numbers and create a perception that rates of infection are higher. Testing people who appear to be healthy would tend to lower the overall rate of positive results, while narrowing testing to people who are sick would raise the overall positive rate, Auerbach said. Why HHS would order such a change quickly became a matter of speculation.

Dr. Carlos del Rio, an infectious diseases specialist at Emory University, suggested in a tweet that there are two possible explanations. One is that it may be driven by testing supply issues that in many parts of the country have caused widely reported delays in results of a week or more, he suggested. In the HHS email, agency officials said that is not the reason, and argued that testing capacity is plentiful. But Dr. Mysheika Roberts, health commissioner for the city of Columbus, Ohio, said testing in her city last month had to be curtailed because of a shortage of reagents used in lab procedures. She agreed with the idea that whatever the federal guidance is, testing decisions ultimately must be made at the local level. But she she was surprised by the change in federal guidance. “I feel so strongly that we should test asymptomatic people when the capacity allows you to,” she said. “And when we were testing asymptomatic people here in Columbus, we were picking up a large number of individuals.”

Another possible explanation for the change is that President Donald Trump simply wants to see case counts drop, and discouraging more people from getting tested is one way to do it, del Rio said in his tweet. Giroir said the change in guidance was passed by consensus by the White House task force without input from Trump or Vice President Mike Pence. “There was no weight on the scales by the president or the vice president” or HHS Secretary Alex Azar, Giroir said.

Dr. Tom Frieden, who was head of the CDC during the Obama administration, said the move follows another recent change: to no longer recommend quarantine for travelers coming from areas where infections are more common. “Both changes are highly problematic” and need to be better explained, said Frieden, who now is president of Resolve to Save Lives, a nonprofit program that works to prevent epidemics. Frieden said he, too, believes HHS forced CDC to post the changes. He called it “a sad day” because “CDC is being told what to write on their website.”

New York Gov. Andrew Cuomo harshly criticized the new CDC recommendations and said the state would not be following the guidance. “Why would you reverse yourself on the quarantine order? Because they don’t want publicity that there is a COVID problem. Because the president’s politics are, ‘COVID isn’t a problem We’re past COVID. It’s all about the economy,’” Cuomo told reporters on a conference call. “What possible rationale is there to say, ’You’re in close contact with a COVID-positive person. And you don’t need a test?’” Cuomo said.

The principal investigator of California’s contact tracing program, Dr. George Rutherford of University of California, San Francisco, agreed. “I hesitated to say public health malpractice,” Rutherford said. “In order to control this, especially in the context of contact tracing, you absolutely have to test people without any symptoms.”