7 things to know now: Attack in Brussels; primary voting; mom charged in daughters' deaths

What to know now:

1. Brussels attack: At least 28 people were killed and scores wounded when explosions tore through the Brussels airport on Tuesday morning.  A second blast was reported at a metro station in the city. Officials  are telling people to stay where they are. According to authorities, shots were heard at the airport prior to the blasts. The explosions happened four days after a suspect in the November ISIS attacks on Paris was captured there.

2. Primaries today: Republicans and Democrats head to the polls today in Arizona, Utah, Idaho and American Samoa as the 2016 primary season continues. Donald Trump is favored to win in Arizona with Ted Cruz polling on top in Utah. On the Democratic side, Bernie Sanders is leading in Utah, and Hillary Clinton is ahead in Arizona.

3. Obama in Cuba: President Barack Obama will continue his visit to Cuba Tuesday, after a day meeting Cuban President Raul Castro and participating in an almost unheard of event in the communist nation – a dual press conference. The two leaders plan to attend a baseball game together Tuesday.

4. FBI vs. Apple:  Federal officials say they believe they have a way to unlock an encrypted iPhone used by the couple who attacked and killed more than a dozen people in San Bernardino, Calif.,  in December. Federal prosecutors said "an outside party" came forward to show authorities a possible way to unlock the phone. A court hearing that could have tried to force Apple to help authorities get information from the phone was canceled Monday.

5. Children killed: The estranged wife of a Ukrainian pianist has been charged in the deaths last week of the couple's two daughters. Vadym Kholodenko discovered his daughters Nika, 5, and Michela, 1, in their beds at their mother's home in Fort Worth last Thursday. They had been stabbed to death. Sofya Tsygankova, 31, was charged with two counts of murder on Monday.