Actress Keira Knightley is reportedly so terrified of a fan who screamed at her during her Broadway show's debut, she has filed harassment documents.

The British star is appearing in Therese Raquin in New York City, with the first night of previews taking place last Thursday (01Oct15).

The performance had only been going 15 minutes when Landon Rust, 29, began shouting at Keira from a mezzanine.

He apparently asked the 30-year-old star to marry him and begged for a response, with Keira and her castmates managing to ignore him.

According to the New York Post, the star was a lot more shaken than she initially appeared.

"She was scared. She wanted to document the incident to start a paper trail..." a law enforcement insider told the publication of Keira's harassment filing, which happened on 2 October.

"If he starts following her around and showing up where she is, then she can get an order of protection against him, but only with a paper trail."

As well as proposing, Landon threw flowers at Keira as she was performing at the Studio 54 theatre on West 54th Street.

Although he continued shouting at her, one onlooker praised the star for not being distracted.

"I would say Keira did a very good job of keeping her composure," Kacey Bange told E! Online.

Security were quick to react to the disturbance too, with Landon removed from the play - although he did manage to get free at one point. When he was eventually detained, he was put in handcuffs and taken to a hospital after saying he felt unwell. At some point he received a misdemeanour harassment summons too, with the New York Post then managing to talk to him.

"I got engaged last night," he said last week (ends02Oct15). "Now that doesn't make any sense and it's not supposed to make sense."

He added that he would be leaving New York and wasn't planning on seeing Keira again.

"If I'm at a party and she's at a party, great," he said. "But I'm not going to try to get on stage with her again - that was a nightmare."