A gunman entered the Borderline Bar & Grill in Thousand Oaks, California, at about 11:20 p.m. Wednesday night and killed at least at least 12 people, including Ventura County Sgt. Ron Helus, Ventura County Sheriff Geoff Dean said early Thursday. Many other people were wounded in the crowded bar, and the gunman is also dead. The FBI's Joint Terrorism Task Force has been sent to the country music bar.

According to Borderline's social media accounts, the bar was hosting an event aimed at college students on Wednesday night. Pepperdine University is in nearby Malibu, and the student newspaper says students from campus were believed to be in the bar when the shooting started. The bar is also popular with students at Moorpark College.

This is a breaking story, and it will be updated as new developments come in. Peter Weber

President Trump may soon have a brand new acting chief of staff.

Over the last few days, Trump has been chatting with allies about who might be able to replace current acting Chief of Staff Mick Mulvaney, two people close to the White House told Reuters. Mulvaney has been acting chief of staff since January, when he stepped in after John Kelly resigned.

Trump isn't happy with how Mulvaney dealt with the fallout from his now-reversed decision to host next year's G7 at his own Miami resort, Reuters says, or how Mulvaney publicly admitted last week that Trump held military aid from Ukraine in order to get Kyiv to investigate a conspiracy theory about the 2016 presidential election. He's also reportedly angry that Mulvaney pushed to bring former Rep. Trey Gowdy (R-S.C.) onto Trump's outside legal team, despite the fact that lobbying rules prevent Gowdy from joining until January.

"The president expressed some concern after Mick's difficult week," one person told Reuters. Two people who have been suggested to take Mulvaney's place have previously turned down the position: Trump's son-in-law and senior adviser Jared Kushner and White House counselor Kellyanne Conway. Another name being floated around is Matthew Whitaker; a Trump supporter, he served as acting attorney general before William Barr's confirmation. Catherine Garcia

Defense Secretary Mark Esper on Monday said some U.S. troops may remain in eastern Syria to ensure that Islamic State fighters do not take over oilfields.

Earlier this month, President Trump said he would pull most U.S. troops out of Syria, which paved the way for Turkey to cross the border and attempt to push back Kurdish forces. As American allies, the Kurds led the fight against ISIS in Syria, losing thousands of fighters in the process.

Esper said the plan is still being worked out, and has not yet been seen by Trump. By leaving some U.S. troops in Syria, it would give Trump "maneuver room," he told reporters. Esper also said that troops leaving Syria will go to western Iraq, and operations against ISIS will continue. During a Cabinet meeting on Monday, Trump said ISIS had once been "all over the place," but he "captured them. I'm the one who did the capturing." Catherine Garcia

CNN host Alisyn Camerota isn't a fan of the new guy.

The network recently hired former GOP Rep. Sean Duffy as a contributor, and in his first appearance on the network on Monday, he was already throwing out conspiracy theories. In particular, Duffy defended White House Press Secretary Mick Mulvaney for saying the White House wanted Ukraine to hand over the DNC email server — something Ukraine certainly doesn't have.

Duffy reiterated Mulvaney's comments from last week where he said the White House withheld aid money from Ukraine to pressure it to hand over the emails hacked in 2016 — an admitted quid pro quo. There's just one problem: "That's a conspiracy theory," Camerota told Duffy. The former congressmember then dug himself deeper into his theory, even trying to bring former Vice President Joe Biden into the mix. Camerota breathlessly egged him on the whole time before blurting out that "Ukraine doesn't have the server." Duffy even agreed Camerota might be right on that point, but to him, the facts didn't exactly matter. Kathryn Krawczyk

The Associated Press believes the Michigan State Spartans have a great chance of becoming the first Big 10 basketball to win the Division I championship since, well, Michigan State in 2000. The Spartans overwhelmingly earned the top spot in AP's preseason college basketball top 25, receiving 60 of 65 first place votes. It's the first time Michigan State's ever been ranked No. 1 in a preseason AP poll, which is surprising given the program's consistent greatness.

The Big 10 is generally one of the country's most competitive conferences, but a national title has remained elusive. Regardless, preseason predictions have pegged the Spartans, led by longtime coach Tom Izzo and senior point guard Cassius Winston, as the team to beat. It's not a surprise — Michigan State went to the Final Four last season and returns Winston, who projects to be one of the best players in the country once again, as well as two other starters in Xavier Tillman and Aaron Henry. They'll also be getting back Winston's classmate and NBA prospect Joshua Langford, who missed most of last season with a foot injury.

There's still a long way to go, of course, and Michigan State will have plenty of competition. Kentucky and Kansas split the remaining five votes and are ranked No. 2 and No. 3, respectively. Duke finds itself the nation's fourth-ranked team to begin the year, but the Blue Devils will be dealing with a lot of turnover. Other teams in the top 10, such as Florida and Michigan State's Big 10 competitor Maryland, also looked poised to go deep into March.

Virginia, the defending champion, will enter the year as the No. 11 ranked team, though it did lose its three star players — De'Andre Hunter, Ty Jerome, and Kyle Guy — to the NBA draft this offseason. See the full rankings here. Tim O'Donnell

President Trump is back to square one.

After seemingly favoring either of his current immigration heads Ken Cuccinelli and Mark Morgan as his new homeland security secretary, Trump was reportedly informed neither will be allowed to take the job without Senate approval. That's because an opinion out of the Department of Justice's Office of Legal Counsel blocks acting heads from ascending to lead a Cabinet department, The Wall Street Journal reports and CNN confirms.

As it stands, Cuccinelli is the acting head of U.S. Citizenship and Immigration Services and Morgan is the acting leader of Customs and Border Protection. They, along with recently resigned DHS acting head Kevin McAleenan, all got their jobs when Trump pushed out Kristjen Nielsen as the head of the department in April.

But in order to rise to replace McAleenan without a Senate vote, they'd have to "either be next in line for a position or hold a Senate-confirmed position," OLC opinion says. Cuccinelli or Morgan could also get the job if they'd served "at least 90 days in the past year under the previous secretary," the Journal writes. The last full-time secretary was technically Nielsen, and Cuccinelli or Morgan didn't work long enough under her, Sean Doocey, head of the White House Presidential Personnel Office, reportedly told Trump in a Friday meeting.

The White House didn't immediately respond to a request for comment. Find out who Trump is considering now at The Wall Street Journal. Kathryn Krawczyk

Sen. Elizabeth Warren (D-Mass.) delivered an education plan Monday as part of her Democratic presidential campaign.

Warren's proposal in total would cost $800 billion, including quadrupling funding for Title I to $450 billion to boost schools with low-income students, $200 billion in grants for student's with disabilities, and $50 billion in school infrastructure.

The latter figure will head to schools that need it the most, Warren's plan notes, arguing "we cannot legitimately call our public schools 'public' when some students have state-of-the-art classrooms and others do not even have consistent running water." The plan also clarifies that money is in addition to funds that would affect schools as laid out in Warren's other plans. For example, she's already explained in her energy plan that she would commit billions to upgrade school buildings to increase energy efficiency and invest in zero-mission school buses, but there'd be no overlap with the newly proposed funding.

Warren's education plan is also significant because it's the last plan she has made that would be funded by her proposed wealth tax, The Wall Street Journal reports. Now, she'll draw up new ways to explain how she'll fund her forthcoming proposals, which the Journal notes, she has done before. Read the full plan here. Tim O'Donnell