Images have surfaced online that appear to show the gunman that killed nine people at an African-American church in South Carolina posing with a gun.
The collection of photographs found on a website also show 21-year-old Dylann Roof burning the US flag and visiting a former slave plantation.
In one image he is shown staring down the camera while sitting on a chair in camouflage trousers holding a gun.
It is unclear who posted the images on the site, which was found on Saturday.
The website also carries a racist manifesto, the provenance of which is also unknown. Internet records suggest the website's domain was registered in February but it is unclear who was behind it.
A law enforcement official, quoted by AP, said the Federal Bureau of Investigation (FBI) was looking into the website.
Data from the images show many of them were taken in April and May this year.
Many of the photographs show Mr Roof posing with the Confederate flag, a symbol used in the US south during the civil war when southern states tried to break away to prevent the abolition of slavery.
It is viewed by many as symbolising the white supremacy advocated by those states at the time.
Former Republican presidential candidate Mitt Romney has joined calls for South Carolina to take down the controversial flag flying outside its capitol building in Columbia.
It follows US President Barack Obama's remark that the flag belonged "in a museum".
Hundreds of demonstrators rallied near the flag on Saturday to demand its removal.
Protesters chanted "Take it down" and sang We Shall Overcome, an anthem of the black civil rights movement.
On Friday, South Carolina's Republican state representative Doug Brannon told MSNBC that he planned to introduce legislation to remove the flag.
Elsewhere, Democratic presidential contender Hillary Clinton has made an impassioned appeal for tougher gun laws, saying that her heart was "bursting" for the families of the victims of the Charleston shooting.
"We can have common sense gun reforms that keep weapons out of the hands of criminals and the violently unstable, while representing responsible gun owners," she told a gathering of mayors in San Francisco.
Mr Roof was arrested on Thursday and charged with the murders of nine African-Americans at the Emanuel African Methodist Church in downtown Charleston.
Police said he spent an hour sitting with parishioners inside the church before opening fire on them on Wednesday evening.
Return to church
Crowds gathered outside the historic church on Saturday to hear pastors from across the US lead prayers. Many travelled hundreds of miles from across the country to pay their respects.
"There was an overwhelming feeling that made me drive here," Monte Talmadge, a 62-year-old army veteran who drove nearly 480km (300 miles) to get to Charleston, told Reuters.
Also on Saturday, a group of congregation members met for the first time in the room where the killings took place.
One of those who attended, Harold Washington, told the Associated Press it was an emotional meeting.
Several rallies were due on Saturday, with one in Charleston organised by the Black Lives Matter movement, which began after the 2013 acquittal of George Zimmerman over the killing of an unarmed African-American teenager, Trayvon Martin.
Up to 3,000 people are also expected to join hands in a march across the Ravanel Bridge, one of the city's main thoroughfares.
The church is due to reopen on Sunday for a service at 09:00 local time (13:00 GMT).
- Cynthia Hurd, 54
- Rev Clementa Pinckney, 41
- Rev Sharonda Coleman-Singleton, 45
- Tywanza Sanders, 26
- Ethel Lance, 70
- Rev Depayne Middleton-Doctor, 49
- Susie Jackson, 87
- Rev Daniel Simmons Sr, 74
- Myra Thompson, 59