The largest police union in the United States has asked Amazon to stop selling T-shirts with the words “Bulletproof: Black Lives Matter” emblazoned on them, the Guardian reported Friday. The national Fraternal Order of Police President Chuck Canterbury penned an open letter to Amazon’s chief executive Jeff Bezos urging the online retail giant to remove the shirt from its website, claiming its message insinuated violence against law enforcement officers. 

Canterbury told the Guardian that Amazon was a “pretty liberal marketer” and hoped that eradicating the shirt would result in “increasing the bonds of trust between the men and women of law enforcement and the communities they serve.”

The police union had sent a similar note to officials at Walmart Tuesday, which had been selling shirts and hooded sweatshirts with the same message written on them. Canterbury said the moves from his department were necessary due to the  “amount of violence demonstrated at Black Lives Matter marches and the fact that eight police officers had been assassinated while protecting Black Lives Matter protests.”

Canterbury was referring to two incidents this summer in which mulitiple police officers were shot in Dallas, Texas, and Baton Rouge, Louisiana. Sgt. Demetrick Pennie, 38, of the Dallas Police Force who is also the president of the Dallas Fallen Officer Foundation, has sued Black Lives Matter over the Dallas incident. In a phone interview with the International Business Times, he called Black Lives Matter a “domestic hate group.”

The pro-Black Lives Matter shirt was still available for purchase on Amazon as of Monday morning. But Walmart announced Tuesday it would stop selling the T-shits and hooded sweatshirts in its stores nationwide.

An article published last week by the conservative Breitbart news website condemned Walmart for selling the pro Black Lives Matter merchandise after it had stopped selling products that displayed images of the Confederate flag in June 2015. 

Roughly 40 percent of people across the United States said they supported the Black Lives Matter movement, while about 30 percent of those who were familiar with the group said they didn’t know its ultimate objectives, according to a Pew Research Center survey conducted between Feb. 29 and May 8.