Kyle Rittenhouse, 17, frequently posted his support for the president and law enforcement on social media, while news footage from a campaign rally in Des Moines, Iowa, also shows the suspected shooter standing near the stage on 30 January. His appearance there was first reported by BuzzFeed News.
Months later, the Illinois teenager allegedly armed himself with a long gun and headed to Kenosha, Wisconsin, as protests continued for a third night following the police shooting of Mr Blake, a black man left paralysed from below the waist after police officers fired several rounds into his back as he got into his SUV. Three of his children were reportedly inside.
Videos from Tuesday's protests show him speaking with police officers moments before the killings. Kenosha Police Chief Daniel Miskinis identified the victims as a 26-year-old Silver Lake resident and a 36-year-old Kenosha resident. A 26-year-old West Allis resident was hospitalised with non-life-threatening injuries.
Rittenhouse was considered a "fugitive of justice" after allegedly fleeing the state, where he awaits first-degree intentional murder charges. He lives in Antioch, Illinois, roughly 30 minutes from Kenosha.
He "fled the state of Wisconsin with the intent to avoid prosecution for the offence", according to the Antioch Police Department.
In a statement, police said that the suspect "is currently in custody of the Lake County Judicial System pending an extradition hearing to transfer custody from Illinois to Wisconsin".
"Our Village of Antioch is deeply saddened by all loss of life," Antioch Mayor Lawrence Hanson said in a statement. "Our hearts and prayers extend to the friends and family who lost a loved one."
He also expressed support for "Blue Lives Matter" on social media, and BuzzFeed confirmed that he was enrolled in a Public Safety Cadets programme through Hindenhurst, Grayslake and Hainesville police departments in Illinois that "offers boys and girls the opportunity to explore a career in law enforcement" through "hands-on career activities", according to the programme's website.
The teen's Facebook page and the cadet programme's website and social media pages have been disabled.
Video footage from the scene in Kenosha on Tuesday night shows a gunman in the middle of the street brandishing a rifle before firing shots that hit multiple people. Witnesses said the gunman was allowed to walk past police without being stopped. In another video, protesters shout at police to call attention to the suspect.
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