While Arbery was still bleeding on the ground, defendant Travis McMichael called him a "fucking nigger," Special Agent Richard Dial of the Georgia Bureau of Investigation said at a court hearing on Thursday.
Arbery was killed Feb. 23 while out jogging in Brunswick. Gregory McMichael, 64, and his son Travis, 34, chased Arbery down the road and shot him, later claiming they had thought he was a burglar.
Dial's information came from William "Roddie" Bryan, a neighbor of Travis and Greg McMichael's, who filmed the shooting.
"Mr. Bryan said that after the shooting took place, before police arrival, while Mr. Arbery was on the ground, that he heard Travis McMichael make the statement: 'fucking nigger,'" Dial said in his testimony.
The incident did not receive widespread national news coverage until May, when video of his killing was made public.
After public outcry, the father and son were charged with murder and aggravated assault.
In May, the Department of Justice said they were also investigating the killing as a possible federal hate crime.