A friend of Charleston church shooter Dylann Roof was arrested Thursday, a source close to the investigation said.
The source did not specify the charges.
Joseph Meek, Jr., 21, was friends with Roof, the white man who opened fire on the historic black church Emanuel African Methodist Church in Charleston on June 17, killing nine people in what authorities have called a racially-motivated attack.
Meek received a so-called "target letter" earlier this month that said he was under investigation for making false statements to investigators and for knowing about a crime before or after it was committed but failing to report it, The Associated Press reported.
RELATED: Charleston church survivor: 'He caught us with our eyes closed'
After the murders, Meek told reporters that he and Roof had been friends in middle school, and that Roof had recently made contact.
Meek said Roof had told him he wanted "segregation" and said "he didn't believe in what the black race was doing to the white race" in the days before the killings.
This article originally appeared on NBCNews.com.