5 Things to Know This Morning

— -- Your look at the five biggest and most buzz-worthy stories of the morning.

1. NYC Building Fire: 4 Critical After Explosion Tears Through NYC Building

Four people were in critical condition and at least 15 others were injured after a building explosion led to a seven-alarm fire in Manhattan's East Village Thursday afternoon.

It was unclear how many people were inside the building when the fire occurred, according to the New York City Fire Department. The incident took place in a bustling area with many restaurants and pedestrians, blocks away from New York University.

"Preliminary evidence suggests a gas-related explosion," said New York City Mayor Bill de Blasio, adding that the investigation is ongoing. He said the incident "appears to have been caused by plumbing and gas work that occurred in 121 2nd Avenue."

2. Germanwings Crash: What We Know About the Flight's Harrowing Final 10 MinutesHere's a breakdown of what we know about Flight 9525's last moments, based on information released by authorities:

At 10:30 a.m., the plane is flying at 38,000 feet.

At some point around this time, the pilot is heard asking the co-pilot to take over the controls. A chair is heard moving and a door is heard closing.

At 10:31 a.m., the plane starts losing altitude.

The co-pilot is alone at the controls, and the accelerated descent is made manually. The pilot is heard knocking on the door and asking over the speaker to enter the cockpit. There is no response from the co-pilot.

The plane’s altitude drops down to roughly 6,000 feet.

Air traffic control can be heard calling, but there is no response. The pilot is heard “violently” banging on the door, as he tries to get back into the cockpit, according to Robin. The co-pilot is heard breathing until the final moment of impact, leading officials to believe he was alive until the crash.

At 10:40 a.m., the plane crashes, and the radar contact is lost.

3. Andreas Lubitz: What We Know About the Co-Pilot

The co-pilot who was at the controls of the Germanwings plane that crashed in the French Alps this week had logged relatively few hours, at least by U.S. standards, prior to the fatal flight.

He has been identified by French authorities as German citizen Andreas Lubitz, 27, and his actions in the final minutes of the flight are believed to have caused the crash, Brice Robin, Public Prosecutor of Marseille, said Thursday at a news conference.

“The intention was to destroy the plane," Robin said, speaking mostly in French.

French Interior Minister Thomas de Maiziere said that investigators are focused on Lubitz' background and motives, though they have started to rule out any connection to a larger plot.

4. Boyfriend of Denise Huskins Says He Was Not Involved in a 'Hoax'

The boyfriend of a California woman who was reported abducted but found safe two days later said Thursday that he was not involved in a "hoax."

"Our client has no responsibility for this kidnapping," said the attorney for Anthony Quinn, the man from whose home the woman was allegedly abducted. "He is in terrible shape -- mental and physical."

Police in Vallejo, California, said on Wednesday they found "no evidence to support the claims" that Denise Huskins was abducted from a home there before she was found alive two days later and more than 400 miles away. The home from which Huskins, 29, was reportedly taken belongs to Quinn, 30.

5. Zac Efron's Girlfriend Sami Miró Opens Up About Their Relationship

Zac Efron has more than 10 million Twitter followers, and a good number of those people are fans who are completely obsessed with him.

His girlfriend, model Sami Miró, admitted that that online attention makes the relationship "definitely different."

"I think that you have to take that [kind of attention] with a grain of salt, and put yourself in other people's positions," she told Elle magazine. "I think that's actually a really big part of it, putting yourself in their shoes, and trying to understand where they're coming from, and then it kinds of makes sense. It kind of just comes with the territory, and I know there's no really changing that, so you have to just embrace it."