SOUTHAVEN, Miss. — Lawyers for the family of a Mississippi man fatally shot by police called Friday on the Justice Department to investigate, saying they believe the man’s death was an execution.

Murray Wells, the attorney for the wife and son of Ismael Lopez, said officers involved in Lopez’s death last weekend in the Mississippi city of Southaven should face criminal charges.

Earlier this week, District Attorney John Champion of northern Mississippi’s DeSoto County said that two officers were present Sunday evening when Lopez was shot at his home in Southaven. According to Champion, police said they fired their weapons after a pit bull dog burst out of the house as they searched for a suspect — and after a man pointed a gun at them through an open door.

But Wells is disputing the account given by authorities. The lawyer said he has hired investigators and has spoken to neighbors of Lopez, an auto mechanic originally from Veracruz, Mexico, who came to the U.S. seeking a better life two decades ago and had never been in trouble with authorities.

Wells has said recently that police didn’t have a warrant for Lopez and were at the wrong address. He also has said Lopez was shot through a closed front door. And Lopez, though a gun owner, didn’t have a gun in his hand when he was killed, according to the attorney.

“We think it was an execution,” Wells said at a news conference Friday at his Memphis office. “Now, when you’re firing through a door, we think it complicates things. Physical evidence says their story isn’t true.”

Local media organizations have reported that a sheriff of a neighboring county said his agency had requested that Southaven police look for a domestic violence suspect who was not Lopez.

Wells said a lawyer from his firm has looked at the body with permission of the man’s family and it appears Lopez was shot in the back of the head. He acknowledged that the determination of where Lopez was shot was that of his firm and doesn’t come from any coroner or doctor. An autopsy report hasn’t been released and authorities said a final autopsy report could take up to eight weeks.

“This man died running away from people who were trespassing on his premises,” Wells told reporters.

The Mississippi Bureau of Investigation is investigating and will turn its findings over to the district attorney, Champion, who can decide whether to pursue charges.

Police have referred questions to the bureau, which did not immediately return a call seeking comment. The DeSoto County’s coroner also didn’t immediately return a call seeking comment.

Wells says police and city officials are covering up facts in the case. He also called for the resignation of the Southaven police chief ans well as the officers involved in the shooting.

Wells says he will send the Justice Department a letter asking federal investigators to step in.

In a statement read in English and Spanish by two of the firm’s lawyers, Lopez’s family said he was a loving husband and father, a hard worker and a mentor to others in the community.

“There is no reasonable explanation about why or how this happened to our Ismael, but we believe his memory demands answers, accountability and justice,” it said.