Slaughter's Twitter page is now set to private, the station reported.
Williams was headed to the store when he was struck and killed by a car, police said Sunday.
WJAX found tweets that the Jacksonville Sheriff's Office said were sent by the driver and included pictures of the dead teen lying on a curb.
"The person tweeting was indeed the driver," said JSO Public Information Officer Melissa Bujeda.
WTEV reported that Slaughter also tweeted song lyrics about drinking "lean" -- a mix of cough syrup and soda - about two hours before the crash was reported.
Bujeda said officers did not conduct a Breathalyzer or blood-alcohol test on Slaughter because officers had no reasonable suspicion he was impaired, the station reported.
According to a traffic crash report, Slaughter was distracted by an electronic communication device.