President Biden, frustrated with congressional inaction on gun violence and seeking to secure the issue as part of his legacy, said on Thursday that he was using his executive authority to improve school preparedness and to stem the tide of untraceable weapons and devices that make firearms more deadly.

Mr. Biden made the announcement at a packed and poignant ceremony in the East Room of the White House, where he was introduced by the mayor of Birmingham, Ala., Randall Woodfin. Mr. Woodfin’s brother was killed by gun violence, and his city has been grieving after a mass shooting left four people dead last week. Scores of activists and gun violence survivors attended.

The event was timed to the first anniversary of the White House Office of Gun Violence Prevention, which Mr. Biden created last year after signing the Bipartisan Safer Communities Act, the first major gun safety bill in nearly 30 years. It was also a chance for Mr. Biden to pass the baton to the official who heads that office: Vice President Kamala Harris, who is leaning into gun violence prevention as an issue as she campaigns to succeed Mr. Biden.