Aaron Carter has surrendered two of his rifles to police after his brother Nick filed for a restraining order against his sibling.

Nick announced he and his sister Angel had filed for a protection order against the Crazy Little Party Girl singer on Tuesday, alleging Aaron had made threats against his pregnant wife, Lauren Kitt, and their unborn child.

"In light of Aaron's increasingly alarming behaviour and his recent confessions that he harbours thoughts and intentions of killing my pregnant wife and unborn child, we were left with no choice but to take every measure possible to protect ourselves and our family," he tweeted, along with the hashtags "#mentalhealth #GunControlNow #GunControl".

In response, Aaron launched a Twitter tirade against his brother, repeating rape and assault allegations against the Backstreet Boys singer. But among the tweets on Wednesday, the 31-year-old revealed he had given two of the guns he allegedly purchased earlier this month back to authorities.

"So today I decided to voluntarily allow the sheriffs department to hold on to two of my rifles (sic). I'm doing this to show my good faith and cooperation with law enforcement. @DOJPH #GunSafety #GunControl," he tweeted.

He also tweeted on Wednesday that police had given him permission to keep his weapons, adding: "The cops came to my house again today. And I am fully allowed to keep my guns. It has nothing to do with that. They wanted to find out and see if the law states that which bit does not and it is my constitutional right (sic). 'So 'BIG BRO' you're NOT gonna win this. I would admit now."

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