A man accused in the shooting death of a police officer is mentally competent to stand trial, a Mississippi judge has declared.

After hearing testimony Thursday, Judge Christopher Schmidt ruled Darian Atkinson, 20, was able to help with his legal defense, The Sun Herald reported.

Authorities said Atkinson walked up behind Biloxi Police Officer Robert McKeithen outside a police station on May 5, 2019, and killed him. Atkinson was later indicted on a capital murder charge.

At Thursday’s hearing, Dr. Chris Lott, a psychiatrist, told the judge that Atkinson said he shot the officer because black people have been oppressed and he had the right to bear arms and act. Lott also said Atkinson’s intellect was within the normal range, and he was polite and forthcoming when questioned.

“He understands the charge,” Lott said. “He understands the possible penalty. He understands the legal process. He understands his role. He gave a … correct factual response to questions regarding his legal situation.”

Lott said there were some concerns though.

“The concern I have here is not with his understanding of the facts of the case, but with the legal strategy and understanding and wishes as far as any legal strategy in his case,” Lott said. “He thinks a jury would understand why he took the action he did.”

Atkinson’s defense attorney, Theressia Lyons, plans to argue insanity, saying her client has a mental and emotional impairment that prevents him from fully understanding his actions the night he shot McKeithen.

Lott noted Atkinson’s family said he began acting strangely after returning from a trip to Texas shortly after graduating high school. Lott said Atkinson told his family things like they needed to turn off the television because people were listening.

Police have said the shooting was premeditated. They say Atkinson walked 8 miles (13 kilometers) from Gulfport to the Biloxi Police Department with the goal of killing an officer. After the shooting, Atkinson called a girlfriend, who told authorities he said he shot McKeithen “because I’m crazy.”

Atkinson’s trial is scheduled for Sept. 20.

Four of his six co-defendants have pleaded guilty to accessory and hindering prosecution for helping Atkinson escape after the shooting.