It remains a difficult case for researchers and it is unclear what charge they will be able to file.
Investigators have struggled for weeks to build a federal murder case on Sicknick’s death while analyzing videos and photographs to try to determine when he suffered his fatal injuries. Investigators determined that early reports suggesting Sicknick had been hit with a fire extinguisher were not true, CNN previously reported.
Several people have been accused of assaulting police officers in the weeks following the attack, but so far none in relation to Sicknick. More than 100 police officers were injured in the melee last month, including at least 15 that required hospitalization, according to a court document.
This story has been updated with background information.
CNN’s David Shortell contributed to this report.