NEW YORK (AP) — Dick's Sporting Goods will immediately stop selling assault-style rifles and ban the sale of all guns to anyone under 21, the company said Wednesday, as its CEO took on the National Rifle Association by calling for tougher gun laws after the massacre in Florida.

The strongly worded announcement from the sporting goods chain that is also a major U.S. gun retailer came as students at Marjory Stoneman Douglas High School in Parkland, Florida, returned to class for the first time since a teenager killed 17 students and educators with an AR-15 rifle two weeks ago.

"When we saw what...