It remains a difficult case for investigators and it is not clear what prosecution they will be able to bring.
Investigators fought for weeks to build a federal murder case for Sicknick’s death while examining videos and photos to try to determine when he suffered his fatal injuries. The investigators determined that the initial reports suggesting that Sicknick had been hit by a fire extinguisher were not true, CNN previously reported.
Several people have been accused of assaulting police officers in the weeks since the attack, but none so far in relation to Sicknick. More than 100 other police officers were injured in the confusion last month, including at least 15 who needed hospitalization, according to court documents.
This story has been updated with basic information.
CNN’s David Shortell contributed to this report.