How would more gun laws have prevented Belmont shooting?

To The Daily Sun,

RE: "Walking a fine line:" (https://www.laconiadailysun.com/news/local/sheehan-case-shows-dealing-with-mental-health-crises-is-delicate/article_03a178a0-b952-11e9-8b02-5f425e3ee284.html")

"On June 13, he pulled a gun on his girlfriend because, he said, she was talking back at him. It wasn’t the first time he assaulted or threatened her.

Hours before he died, he pulled a gun and assaulted his sister, and also pulled a gun on his mother.

Sheehan had a felony criminal record, and so was not allowed to possess firearms. The guns he had in his possession he had taken from his girlfriend, and she had purchased the pistol he was holding up to his chin went officers shot him. She told investigators she bought it under duress.

“Looking at the long criminal history of Mr. Sheehan, none of us should be surprised that his violence and dangerous behavior escalated so drastically,” said Shauna Foster, program manager at New Beginnings in Laconia."

Tell me again how "universal background checks" and "banning assault weapons" imposed on law-abiding citizens would have prevented this incident.

Jack Potter

Meredith