Two people misidentified online as suspects in the fatal shooting of US right-wing activist Charlie Kirk said they fear for their safety as misinformation spreads, while the manhunt for the real killer continues.

Michaela, a 29-year-old woman from Washington state, told AFP she became "really scared" after her photo circulated in posts falsely naming her as the shooter.

"I’m getting witch-hunted online," she said.

"Some people want to enact vigilante justice on me."

Michaela, who works as a paralegal, said she was at home in Washington when Kirk was killed at Utah Valley University.

Screenshots of her bank transactions and phone location confirmed her whereabouts, and her roommate corroborated her account.

She said her profile picture was likely linked to the shooting because it appeared in searches tied to another X user who posted about Kirk's event.

Michaela has contacted the FBI, which released images of a person of interest on Thursday and confirmed that the presumed murder weapon was recovered.

She has also posted online to clarify she is not a suspect, but her image continues to circulate, often shared by conspiracy-driven accounts.

She said she has received threats filled with slurs.

In Canada, 77-year-old retired banker Michael Mallinson said he too was falsely accused after his photos were matched to footage of a man briefly detained by police.

Mallinson said he learned of the hoax when his daughter called him in panic, warning that she had received abusive messages.

"I have absolutely nothing to do with this," he said.

"I was horrified and shocked."

He has since deleted his social media accounts, alerted police, and sent friends and relatives messages explaining the situation.

"It's my image, it's my name, but it's not me. I worry about longer-term ramifications. That stuff stays on social media forever," he said.