Reuters:
U.S. says Capitol rioters meant to 'capture and assassinate' officials - filing
The detention memo, written by Justice Department lawyers in Arizona, goes into greater detail about the FBI’s investigation into Chansley, revealing that he left a note for Pence warning that “it’s only a matter of time, justice is coming.â€
“Strong evidence, including Chansley’s own words and actions at the Capitol, supports that the intent of the Capitol rioters was to capture and assassinate elected officials in the United States government,†prosecutors wrote.
That letter, in itself, doesn't seem like iron-clad proof of plans to capture and assassinate. It's unfortunate they're not listing any periphery information that supports this headline (like the nooses hung up outside).
WaPo ran a similar headline, only additionally mentioning this:
One man, for instance, was arrested and accused of carrying a pistol on the Capitol grounds. Others wore tactical gear or brought zip ties, which can be used as handcuffs, officials said. And another was arrested after his truck was spotted nearby, allegedly with 11 molotov cocktails inside.