UK "Downton Abbey" viewers already witnessed the horrifying death in season 3 this past Christmas, but for US viewers they received the shock during the finale on Sunday, Feb. 17.

As fans now know, Lady Mary gave birth to a healthy baby boy in the Season 3 finale. Right after meeting his newborn son, Matthew left, going on a joy ride and obviously ecstatic about his growing family. Unfortunately that car ride and joyous moment took a turn for the worst when Matthew was forced to swerve to avoid hitting another car. When the camera cut back to Matthew, the car had flipped and he was lying lifeless with blood running from his ears.

A definite shocking ending, fans of the BBC series already knew that actor Dan Stevens had planned to leave the series. However, "Downton Abbey" creator Julian Fellowes told Entertainment Weekly that Matthew's death was something they strongly discussed in the writer's room.

"I think we weren't really faced with an alternative storyline, because I think audiences would not have accepted Mary and Matthew becoming estranged," he said of the couple. "It was too big a journey that the audience had been on with this relationship. The idea that he would go off on the journey and she wouldn't go with him, or the idea that he would leave her or she would leave him, I think that would have been so disappointing and unbelievable to an audience. The only course open to us was that the character had to die."

But with Matthew now gone, where does that leave Lady Mary and their son?

According to Fellowes, Matthew's spirit will continue through his child, "but we don't know what form the future is going to take."

"The last image that everyone's been left with is, 'What's gonna happen to this Mary?' and so that's obviously going to be the spine of the next season, how she rebuilds her life," Fellowes continued. "She's an eligible young widow"

As we previously reported, "Downton Abbey" is already looking to cast a new love interest for Lady Mary. A report from indicates that Mary's new man could be named Lord Anthony Gillingham, a 30-something-year-old with a "winning personality." It appears that the "winning personality" of Lord Gillingham's will win over Lady Mary, because outlets are already reporting "talk" of a return for season 5.

But just because a new love interest is on the table doesn't mean that Lady Mary is ready to move on past Matthew.

"I imagine Mary will not be able to move on very quickly," actress Michelle Dockery previously told Entertainment Weekly. "It will be very difficult to replace the love of her life. The thing is that for the third [season] Mary was largely happy and content and they got the money to save Downton. I find myself smiling more often as the character and my guess is that I will not be seeing that smile again for awhile. I'm sure she won't come out of mourning too quickly."

What would you like to see happen with Lady Mary in Season 4 of "Downton Abbey"? Sound off in the comments section below.

Love "Downton Abbey"? Also check out:

'Downton Abbey' Season 4 Spoilers: Who Will Be [Spoilers] New Love Interest?

'Downton Abbey' Season 4 Spoilers: More Scoop On [Spoiler's] Love Life!