Chubb, the underwriter behind insurance policies that covered National Rifle Association members sued over shootings, says it decided to end the coverage long before a teenager carrying a semi-automatic rifle killed 17 people at a south Florida high school.

The Zurich-based firm joins companies from First National Bank of Omaha to rental car businesses like Avis and Enterprise pulling away from the powerful gun-lobbying group, which is fighting tighter regulation after killings in Broward County, Fla., and shooting sprees in Texas and Las Vegas.