Federal, state, and local authorities have dramatically increased security ahead of President-elect Donald Trump’s Monday inauguration but have still issued warnings to anyone who plans to be in Washington, D.C., to be on the lookout for potential “lone wolf” attacks.

Trump’s swearing-in ceremony has been moved indoors, ostensibly due to a forecast of extremely cold temperatures in the nation’s capital, but authorities say there are still concerns over potential attacks, especially after Trump was targeted twice during his campaign, nearly losing his life when he was nicked by a sniper’s bullet in Butler, Pa., in July.

“Lone wolf actors are always extremely significant to law enforcement personnel who are trying to safeguard the people that are attending these events,” Sgt. Matthew Fagiana, a retired patrol commander with more than 25 years of experience with law enforcement, told Fox News Digital.

“One of the reasons that they’re always a concern is they can be very unpredictable, and they are driven by extremist ideologies,” he added.

The threat of potential lone wolf attackers rose after a machete-wielding individual attempted to pass through a magnetometer and X-ray security checkpoint while Trump was paying respects to former President Carter. The 44-year-old suspect was granted conditional pre-trial release following a hearing just days before Trump’s inauguration, Fox noted.