UTAH, USA — Authorities are still trying to learn more about what motivated the fatal shooting of Charlie Kirk at a college in Utah, as the conservative activist’s family plans a memorial next week to his life and legacy.

Tyler James Robinson, 22, of Washington, Utah, was arrested on suspicion of aggravated murder and other felony offenses. Prosecutors are drawing up formal charges that could be filed early next week, when he will make his first court appearance.

Investigators have spoken to Robinson’s relatives and carried out a search warrant at his family’s home in Washington, about 240 miles (390 kilometers) southwest of Utah Valley University, where the shooting took place.

Here are things to know about the killing:

Authorities have not provided many details about why they think Robinson carried out the attack on Kirk.

“There clearly was a leftist ideology,” Utah Gov. Spencer Cox said on NBC’s “Meet the Press,” noting that family and friends described Robinson’s politics as veering left in recent years. They recounted to authorities a dinner table conversation in which he mentioned Kirk’s upcoming visit to Utah Valley University and they discussed whether the activist was spreading hate.

Cox said Robinson is “not cooperating” and that friends paint a picture of someone radicalized in the dark corners of the internet. However, Cox stressed on several Sunday morning news shows that investigators are still trying to pin down a motive for the attack on the father of two and confidant of President Donald Trump.

State records show Robinson is registered to vote but not affiliated with a political party and is listed as inactive, meaning he did not vote in the two most recent general elections. His parents are registered Republicans.

Ammunition found with the weapon used to kill Kirk was engraved with taunting, anti-fascist and meme-culture messages. One bullet casing had the message, “Hey, fascist! Catch!” Cox said.

He grew up around St. George, in the southwestern corner of Utah, between Las Vegas and natural landmarks including Bryce Canyon and Zion National Parks.

Robinson became a member of The Church of Jesus Christ of Latter-day Saints, known widely as the Mormon church, at a young age, church spokesperson Doug Andersen said.

Robinson has two younger brothers, and his parents have been married for about 25 years, according to social media posts. Online activity by Robinson’s mother reflects an active family that took vacations to Disneyland, Hawaii, the Caribbean and Alaska.

Like many in that part of Utah, they frequently spent time outdoors — boating, fishing, riding ATVs, zip-lining and target shooting. A 2017 post shows the family visiting a military facility and posing with assault rifles. A young Robinson is seen smiling as he grips the handles of a .50-caliber heavy machine gun.

A high school honor roll student who scored in the 99th percentile nationally on standardized tests, he was admitted to Utah State University in 2021 on a prestigious academic scholarship, according to a video of him reading his acceptance letter that was posted to a family member’s social media account.

But he attended for only one semester, according to a university spokesperson. He is currently enrolled as a third-year student in the electrical apprenticeship program at Dixie Technical College in St. George.

Robinson’s partner is transgender, Cox said. Some politicians have pointed to that as a sign Robinson was targeting Kirk for his anti-trans views, but authorities have not said whether it is relevant as they investigate Robinson’s motive. Cox said the partner has been “incredibly cooperative,” and “had no idea that this was happening.”

It prompted calls for greater civility in the country’s political discourse, especially on social media. But many people have made comments about Kirk and the shooting that brought consequences. Numerous workers have been fired for their comments on Kirk’s death, among them MSNBC political analyst Matthew Dowd, who lost his job shortly after on-air comments about Kirk.

It’s not the first time people have lost jobs over things they say publicly, but the speed of the firings has raised questions about worker rights versus employer rights.

Florida Gov. Ron DeSantis’ education commissioner warned teachers in the state that making “disgusting” statements about Kirk’s assassination could draw sanctions, including the suspension or revocation of their teaching licenses.

A conservative internet personality who is embedded with immigration agents in Chicago filmed a video outside Illinois Gov. JB Pritzker’s private home in which he urged viewers to “take action” after Kirk’s assassination. Pritzker’s office said his security has been increased in recent days.

Partisans have been fighting over who’s to blame for Kirk’s death, but experts on political violence say many of those who commit such crimes seem to act on beliefs that don’t map clearly onto partisan lines. They say the broader political environment is more important: The more heated the atmosphere, the more likely it is to lead unstable people to commit acts of violence.

Turning Point USA, Kirk’s conservative organization, will hold a memorial for him Sept. 21 at State Farm Stadium outside Phoenix, where the Arizona Cardinals play.

Kirk’s casket arrived Thursday in his home state aboard Air Force Two, accompanied by Vice President JD Vance.

His widow, Erika Kirk, vowed to continue his campus tour and his radio and podcast shows.

“To everyone listening tonight across America, the movement my husband built will not die,” she said Friday in a livestreamed video. “It won’t. I refuse to let that happen.”

On Sunday, Kirk was memorialized at Dream City Church in Phoenix, where he hosted one of his “Freedom Night in America” gatherings. Attendees viewed clips of the conservative activist discussing his desire to be “remembered for courage for my faith.” Angel Barnett, a church pastor, called on the crowd to honor Kirk by carrying on his message.

Flowers, U.S. flags and handwritten messages were left at a makeshift memorial for Kirk at Utah Valley University’s main entrance. The school has said there will be increased security when classes resume Wednesday.

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