The Associated Press and the USA TODAY NETWORK - Tennessee

A note found in the Nissan Xterra of a man charged in a deadly Nashville church shooting referenced retaliation for a white supremacist's massacre at a black church two years ago in Charleston, South Carolina, law enforcement officials told the Associated Press.

Police say Emanuel Kidega Samson, 25, fatally shot one woman and injured seven others in an attack Sunday at the Burnette Chapel Church of Christ. While police have not released a motive for the attack, the note could offer a glimpse into his mindset.

The Associated Press in Washington, D.C. has not viewed the note, but it was summarized in an investigative report circulating among law enforcement.

The report said that "in sum and in no way verbatim," the note referenced revenge or retaliation for Dylann Roof, the white supremacist who killed nine black worshipers at a South Carolina church in 2015 and has since been sentenced to death.

It wasn't clear what Samson, who is black, is alleged to have written about the Roof shooting, or whether his note contained other details that might also speak to a motivation or state of mind.

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Two law enforcement officials read portions of the report to the Associated Press on condition of anonymity because they were not allowed to publicly discuss an ongoing investigation.

Local authorities have not commented on the note

Metro Nashville police on Friday would not comment on the new information.

"We do not anticipate additional announcements concerning the Burnette Chapel Church of Christ (shooting) as the case remains under investigation," police spokesman Don Aaron said.

Spokespeople for the Nashville district attorney's office, the FBI and U.S. attorney's office also declined to comment, citing the ongoing investigation. Samson's public defender did not immediately respond to a request for comment.

Samson is charged with murder, but other charges are expected.

Samson told police he was at Burnette Chapel and "acknowledged that he fired, quote, 'at the church,'" police Chief Steve Anderson said Monday at a news conference. "That’s the extent of our information that we’ve obtained from him at this point."

Minister Joey Spann, who was shot in the chest and the hand, has expressed doubt when asked if the shooting was racially motivated. During a Tuesday news conference at Vanderbilt University Medical Center, he said his church was older and mostly white, but he added that the congregation included "some black members."

"I don’t know where they would get that this was racially motivated," Spann said. "I don’t know if he had another belief system. I don’t know. I just find that out from listening to you all.”

Police said Samson had four guns with him at the church. He took .40-caliber and 9mm handguns inside the church, while leaving a .22-caliber pistol and an unloaded semi-automatic AR-15 rifle in his SUV, police said. He wore a tactical vest and brought three additional magazines of ammunition into the church, police said.

Samson fired 12 rounds from the .40-caliber handgun during the attack, according to the police.

Melanie Crow, a 38-year-old mother of two shot dead in the church parking lot, was buried Thursday. Presiding over an emotional funeral, Pastor Mike Thomason urged those in attendance to live out their faith by forgiving Samson.

Spann was released from the hospital Thursday, according to a friend and colleague. Vanderbilt said four shooting victims were still at the hospital Friday.

Motive and background will be key in civil rights investigation

Hours after the attack federal authorities opened a civil rights investigation.

Several former U.S. attorneys recently told the USA TODAY NETWORK - Tennessee why such an investigation is necessary and what law enforcement could learn from the probe.

"Churches, synagogues and mosques are special places, and historically protecting them has been a top priority of federal prosecutors," said former U.S. attorney Jerry Martin.

Former Civil Rights Division attorney Jonathan Skrmetti said investigators do not need to prove that race or religion were the sole motivating factors for the attack. As long as any hate is detected in the suspects' background, Skrmetti said, the crime could fall under federal civil rights statutes.

"A lot involves talking to people close to the attacker, searching the home for any sort of propaganda, journals or any other evidence that would reflect a serious hostility toward a particular race or religion," Skrmetti said.

Samson's case has begun making its way through the court system. Attorneys will meet on Oct. 6 to discuss scheduling of upcoming hearings.

Sadie Gurma–n and Eric Tucker from The Associated Press and Dave Boucher, Natalie Neysa Alund, Holly Meyer and Adam Tamburin from the USA TODAY NETWORK - Tennessee contributed to this report.