A makeshift memorial sits near the spot where 18-year-old Michael Brown was shot and killed by a police officer on October 10, 2014 in Ferguson, Missouri. (Scott Olson/Getty Images)

Forensic evidence shows Michael Brown’s blood on the gun, on the uniform and inside the car of Ferguson police officer Darren Wilson, law enforcement officials said, information they believe potentially corroborates the officer’s story that the unarmed 18-year-old tried to take his gun.

The evidence will make it harder for the Justice Department to prosecute Wilson on federal charges that he violated Brown’s civil rights, said the officials, who spoke on the condition of anonymity because of the sensitivity of the case.

Such evidence would also make it difficult for a county grand jury to indict Wilson on state charges, such as murder or manslaughter, said county sources who also are prohibited from talking on the record about the pending case.

The St. Louis County police, the FBI and a county grand jury are investigating the shooting. The Justice Department is investigating Ferguson and St. Louis County policing practices and whether they have violated the rights of residents.

Justice Department spokeswoman Dena Iverson declined to comment.

Wilson, who is white, fatally shot Brown, an African American, on Aug. 9 in the majority-black St. Louis suburb of Ferguson.

The three-minute encounter on a sunny Saturday afternoon has rocked the metro area, which remains on edge as it faces continued protests and waits for the grand jury to decide whether Wilson should face any charges in Brown’s death.

The New York Times first reported the forensic evidence Friday, citing “government officials briefed on the federal civil rights investigation.”

Officials who spoke to The Washington Post on Saturday said the forensic evidence supports Wilson’s account that a scuffle occurred at the police vehicle, that Wilson feared for his life and that Brown went for, or lunged for, his gun. There were two shots fired in the vehicle, including one that hit Brown’s arm, an official said.

Wilson, who has not spoken publicly since the shooting, testified before the grand jury last month. His lawyer, James P. Towey Jr., did not return a call seeking comment Saturday.

Benjamin L. Crump, a lawyer for Brown’s family, also could not be reached for comment.

He told the Times, however, that Wilson’s word isn’t “gospel,” and that he should be indicted and go to trial.

“The officer’s going to say whatever he’s going to say to justify killing an unarmed kid,” Crump told the Times. “Right now, they have this secret proceeding where nobody knows what’s happening and nobody knows what’s going on. No matter what happened in the car, Michael Brown ran away from him.”

It has never been in question that there was an altercation. Wilson was inside the vehicle, and Brown was at the driver’s window. From the earliest days police have said that Brown scuffled with Wilson and that a shot was fired in the vehicle.

In those first police accounts, St. Louis County Police Chief Jon Belmar said that Brown “allegedly pushed” Wilson back into the car after Wilson tried to open the door. Brown, police said, then “physically assaulted” Wilson and went for the gun. Wilson fired inside the vehicle, they said. Wilson then got out and killed Brown, Belmar said. Police said Wilson feared for his life because Brown charged him on the sidewalk.

Dorian Johnson, the 22-year-old who was with Brown when they encountered Wilson, gave another version of events: Wilson encountered them in the street and ordered them onto the sidewalk. Wilson drove past, then backed up and opened the car door so forcefully that it bounced against the two men. Wilson, still in the car, then grabbed Brown by his collar. Brown was trying to free himself and never tried to get the gun. Wilson drew his gun and threatened to shoot, then it went off. Johnson and Brown then ran.

Several other witnesses recounted activity at the car, but each said they were unclear about the nature of that encounter. They have offered varied though fundamentally similar versions of what happened afterward. Brown, witnesses said, was fleeing when Wilson opened fire on the street. After being hit by a bullet, Brown turned around with his hands up, trying to surrender, when the officer shot him several more times, they said.

Exactly how high Brown’s hands were has been inconsistent in the accounts, and at least one witness said that after Brown was shot, he appeared to take a step toward Wilson. That witness said, however, Brown had his arms around his stomach before hitting the ground.

Brown was shot at least six times, according to three autopsies.

On Saturday, law enforcement officials declined to discuss what happened outside Wilson’s vehicle. St. Louis-area authorities declined to comment Saturday.

Protests were explosive after the shooting, when demonstrators squared off against police who used tear gas and rubber bullets to try to disperse crowds. Images of police patrolling the streets during the day and clashing with demonstrators at night shocked many and drew concern from the White House and some Washington lawmakers.

Some protest organizers said they were unmoved by the forensic details, noting there was no explanation provided of why Wilson continued to fire at Brown, who witnesses said was fleeing.

“It [does] make us more convinced that there’s not going to be an indictment,” said activist Deray McKesson.

A grand jury decision is expected sometime in November, according to the St. Louis County prosecutor’s office.

Kimberly Kindy and Wesley Lowery contributed to this report.