The suspect accused of assassinating conservative activist Charlie Kirk is set to face charges in the coming days as Utah residents remember the alleged killer as a person who was "very quiet" and "kept to himself."Tyler Robinson, 22, was taken into custody Thursday on suspicion of aggravated murder, "felony discharge of a firearm causing serious bodily injury" and "obstruction of justice capital/first degree felony conduct," according to a probable cause affidavit obtained by Fox News. He was ordered by a judge to remain held without bail, and the Utah County Attorneys Office said it plans to formally charge Robinson on Tuesday, Sept. 16."I know for some people when their identities come out, and theyre labeled as a shooter, everyones like, You could tell. And hes not one of those people," Jaida Funk, a 22-year-old who lives in the same neighborhood as Robinson, told The Associated Press. She said Robinson's arrest in the suburb outside St. George was "completely unexpected."Robert Sylvester, who has lived on the same street as the Robinson family for about six years, told the AP that he last saw Tyler Robinson a couple years ago as they both helped fix a leaky pipe at a neighbors home. He described the family as "pretty quiet," mentioning the suspects father keeps busy as a contractor and that, "Theyre not unlike most families."COMPLETE COVERAGE OF CHARLIE KIRK Utah State University confirmed to Fox News on Friday that Robinson "briefly attended Utah State University for one semester in 2021."Hes now enrolled as a third-year student in the electrical apprenticeship program at Dixie Technical College in St. George, according to the AP.Durban Mickelson said to the news agency that Robinson frequently bought supplies from a store where he worked and didn't stand out."He wouldnt really talk to you unless you said something to him," Mickelson added. "Just always very quiet, kept to himself."LEGAL ANALYST CALLS FOR MORE ARRESTS IN CHARLIE KIRK ASSASSINATIONIn addition to state charges, there are active discussions and preparations underway to file a federal charge or potentially multiple federal charges againstRobinson, a source said to Fox News on Friday.State and federal court records do not show any prior criminal cases involving him, the AP reported.Erika Kirk, the widow of the late Charlie Kirk, also gave an emotional tribute to her husband on Friday and declared that his mission will not end at Turning Point USA's headquarters."To everyone listening tonight across America, the movement my husband built will not die," Erika Kirk said in her first public statement since her husband's assassination on Wednesday at Utah Valley University."It won't. I refuse to let that happen No one will ever forget my husband's name. And I will make sure of it. It will become stronger, bolder, louder and greater than ever. My husband's mission will not end. Not even for a moment," she added. "My husband's voice will remain, and it will ring out louder and more clearly than ever. And his wisdom will endure."Fox News Alec Schemmel, David Spunt, Paul Mauro and The Associated Press contributed to this report.