Seven other people have been charged in connection with the plot.

CHICAGO (WLS) -- An eighth suspect allegedly tied to the group that plotted to attack the White House's UFC event earlier this month has been arrested and charged by federal prosecutors in Chicago, according to the Department of Justice.
Alexander Mercado, a 20-year-old Chicago man, was arrested on Thursday and charged with obstruction of justice.
He allegedly deleted the Signal app on his phone after being contacted by an FBI agent on June 13, one day before the UFC event.
According to an indictment, the agent asked Mercado in a telephone call whether he planned to travel to Washington, D.C. to help with the attack, which Mercado denied.
Mercado later allegedly did not respond to follow-up calls attempting to reach him, and investigators found he uninstalled the Signal app on his phone, which led all of his data related to his messages in the group being deleted.
Seven other people have been charged in connection with the plan.
Mercado is due in court in Chicago at 3 p.m. Friday. He faces up to 20 years in prison, if convicted.
An attorney for Mercado could not immediately be reached as of Friday afternoon.
The video in the player above is from a previous report.
ABC News contributed to this report.