The man broke through the audience and sprayed Omar with vinegar as she spoke at Minneapolis City Hall on January 27. The speech took place in connection with the widespread protests against immigration police ICE in the city. She was not injured and chose to continue speaking.
The 56-year-old man said he had "blurry" memories during questioning and has not given any further explanation.
Ilhan Omar, who was elected to the House of Representatives in 2018, came to the United States as a teenager as a refugee from Somalia.
She has been verbally attacked several times by President Donald Trump, not least in his remarks against Somalis in her home state of Minnesota in December last year.
