Stocks racked up more losses on Wall Street Tuesday as a trade war between the U.S. and its key trading partners escalated, wiping out all the gains since Election Day for the S&P 500.

Kroger Chairman and CEO Rodney McMullen is stepping down after an internal investigation into his personal conduct.

The chief executive officers of Kroger and Albertsons have insisted that merging would allow the two supermarket companies to lower prices and more effectively compete with retail giants like Walmart and Amazon.

Grocers Kroger and Albertsons are selling more than 400 stores and other assets to C&S Wholesale Grocers in an approximately $1.9 billion deal as part of their efforts to complete their merger.

U.S. senators from both parties have expressed skepticism that a proposed merger between grocery giants Kroger and Albertsons will lower prices for consumers.

Amazon is looking to offer an average starting wage of more than $18 per hour to fill some transportation and fulfillment roles, with some of the positions receiving up to $22.50 hourly.