Walmart on Wednesday became the second major national retailer to announce changes for firearms and ammunition purchases, in the wake of a school shooting that left 17 people dead.

In a statement, the company said they will raise the age restriction for gun and ammunition purchases to 21 “as quickly as possible.”

Walmart said its decision came after the company reviewed its firearm sales policy in light of the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, where the teenage gunman used an AR-15 rifle. The statement said the company takes “seriously our obligation to be a responsible seller of firearms” and also emphasized its background of serving “serving sportsmen and hunters.”

In announcing the change in policy, the company said it had processes in place to make sure it was applied for online sales.

Dick’s Sporting Goods also said Wednesday that the company will immediately end sales of all “assault-style” rifles in its stores, will no longer sell high-capacity magazines and will not sell guns to anyone younger than 21 regardless of local laws.

The decision by Dick’s drew immediate — and passionate — reaction on social media. By midday, the number of Twitter messages containing the company’s name had jumped 12,000 percent from the average over the previous 10 days, according to Sprout Social, a social media management, advocacy and analytics software platform.

About 79 percent of the tweets had a positive sentiment, according to Sprout, and a spokesman for Dick’s said the company had received an overwhelmingly positive response to its decision. But the company’s critics posted their plans to no longer shop at the retailer, some closing their tweets with “#boycott.”