Citigroup put new restrictions on firearm sales by its business customers, the company said Thursday, making it the first bank to announce changes to its policies in the wake of the school shooting in Florida.

Citigroup will require its clients and business customers not to sell a firearm to anyone who hasn't passed a background check or anyone under the age of 21. They also will not allow its customers to sell what are known as bump stocks and high-capacity magazines. Businesses who do not comply with these new restrictions will have their Citi banking relationship eventually wound down.

"We don't have the perfect solution but we have come to the conclusion that we must do our part to keep guns out of the hands of those who wish to do harm," said Ed Skyler, executive vice president of global public affairs at Citi, in a blog post.

The restrictions apply to Citi clients with credit cards backed by Citigroup or bank with the New York company, be it traditional banking services or activities like raising capital.

Citi will also be reviewing any banking relationships it might have with gun manufacturers, the bank said in a statement Thursday.

Several companies have made changes to their policies in recent weeks following the Parkland school shooting. Delta and United airlines have ended their discount programs they offered with the National Rifle Association, and retailers like Dick's Sporting Goods announced they would no longer carry assault weapons and high-capacity magazines.