Federal prosecutors charge man accused of spraying Rep Ilhan Omar at town hall

Right before the attack, Omar called for the resignation or impeachment of Homeland Security (DHS) Secretary Kristi Noem, following multiple fatal shootings involving federal immigration enforcement agents in Minneapolis.

The criminal complaint featured an image of the syringe that federal prosecutors said was used by Kazmierczak in the incident. 

It cited a Minneapolis Police Department officer as saying that a hazmat specialist "field tested the substance from the syringe and determined it was water and apple cider vinegar."

"The substance was sent to a state laboratory for further testing and analysis," the complaint added. 

"An MPD Detective Sergeant reviewed body worn camera footage of MPD's arrest of Kazmierczak. The detective noted that Kazmierczak made a spontaneous utterance to the effect of 'I squirted vinegar' at the time he was being arrested," it continued.

The complaint also said that on Wednesday, an FBI special agent interviewed a close associate of Kazmierczak who "stated that several years ago, Kazmierczak was speaking to the person on the phone about Representative Omar and said, 'Somebody should kill that b----,' referring to Representative Omar."

Fox News' Jessica Sonkin and Alexandra Koch contributed to this report.