Walmart on Tuesday announced major changes to its stance on ammunition sales, following two deadly and “horrific” shootings at Walmart stores over the summer.

The retailer is calling on the government to do more in the wake of a larger wave of mass shootings across the country, including one as recently as this weekend in Odessa, Texas.

Walmart is also asking customers at Walmart and Sam’s Club to no longer openly carry firearms in stores, in states where “open carry” is allowed, unless authorized law enforcement officers are present.

At the end of July, there was a deadly shooting at a Walmart store in Mississippi, followed by another in August at a Walmart in El Paso, Texas — where 22 people were killed.

Here is the full memo from CEO Doug McMillon sent to Walmart employees on Tuesday:

Next steps in response to the tragedies in El Paso and Southaven

A month ago, in El Paso, Texas, a gunman with an assault-style rifle launched a hate-filled attack in our store, shooting 48 people resulting in the loss of 22 innocent lives. Just a few days prior, two of our associates were killed by another associate in our store in Southaven, Mississippi. And hours after the shooting in El Paso, our country experienced another mass shooting in Dayton, Ohio. This weekend brought tragedy to Midland and Odessa, Texas.