By Nicole Chavez and Tony Marco

CNN

CNN (CNN) -- A Mississippi man who was killed by police in an apparent address mix-up was shot in the back of the head, a family attorney said.

"It is so troubling to learn that not only this man died but that this man died running away from people who were trespassing on his premises after he was in bed lawfully," Murray Wells, an attorney representing the family of Ismael Lopez, told reporters.

Lopez, a 41-year-old car mechanic, was at his Southaven home late Sunday when the deadly police shooting unfolded, Wells said.

Police were looking for a man suspected of assaulting a woman at a gas station in nearby Tate County, according to an incident report. But authorities said the officers responded to the wrong address.

In a Friday news conference, Wells said an independent investigation commissioned by his firm revealed that Lopez died of a single bullet to the back of the head.

"Our conclusion is not a conclusion of the coroner's office but it is very simple to understand what happened when you look at the physical evidence," he said. "It couldn't be any clearer."

A coroner's report has not been released.

Conflicting accounts

Since the shooting, Wells and the DeSoto County District Attorney have given multiple versions of what happened when police showed up at Lopez's residence.

DeSoto County District Attorney John Champion said Southaven police officers knocked on the door of the residence to ascertain if it was the correct location, but the Lopez family didn't hear the knock. He said they only heard their dog barking, and Ismael Lopez went to find out why.

Police officers say that when Lopez opened the door, his pitbull charged at them, and they shot and wounded the dog. When they looked up, Lopez was pointing a gun at them, Champion said. The officers commanded him to lower the weapon, and fatally shot him when he did not comply, Champion said.

The Lopez family attorney said police shot through the door of the home, killing Ismael Lopez, who was unarmed. Wells said bullet holes can be seen through the front door.

There were two guns in the house, Wells said, but none were near Lopez's body. The man's wife told Wells he didn't hear the officers' voices.

Southaven police has not released their police incident report and they would not comment on the status of the officer or officers involved in the case. On Friday, Southaven Police Department Chief Steve Pirtle declined to respond to Wells' allegations.

CNN has reached out to the Mississippi Bureau of Investigation, which is handling the police shooting investigation.

'No reasonable explanation'

As the investigation continues, the Lopez family attorney is now asking for the Department of Justice to look into the case because he believes criminal charges should be filed. He also called for the resignation of the Chief of Police, all officers involved in the fatal shooting and any politicians who may have given false information about what happened.

"What we've heard since this case started over, and over again are stories of bad acting by the Southaven Police Department," Wells said.

The Lopez family remembered him as "a loving husband, guiding father, mentor to the youth in this community and a hard worker," in a statement released through their attorney.

"There is no reasonable explanation about why or how this happened to our Ismael but we believe his memory demands answers, accountability, and justice," the statement said. "We will not rest until we know the truth."

CNN's Nick Valencia, Paige Levin, Samira Said and Charles Levin contributed to this report.

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