Again, nothing mentions the Capitol Building itself (Capitol Grounds and Buildings cover a lot of spaces) and it's not like it is unusual for weapons to be seized https://www.nbcwashington.com/news/local/us-capitol-police-s...
COUNT TWO On or about January 6, 2021, within the District of Columbia, CHRISTOPHER ALBERTS, did unlawfully and knowingly enter and remain in the United States Capitol and grounds, a restricted building and grounds, without lawful authority to do so."