I did a bit more enhancement on the Walmart pic which clearly shows that there is a big black bag in front of the blue object. The blue object looks soft now. There is clearly a shine coming off of the bag & object. In fact, the bag looks almost like a Turkey.
Also, since the police obviously know what was purchased and aren't releasing that information, I think it is reasonable to suggest that this picture was taken BEFORE the murder. This man does not look like someone who just committed a murder, and the number of bags in the cart kinda suggests a food shop. If this was a picture of stuff they bough AFTER the murder, the police would tell us what they bought since these items could be used to identify them.