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:

What do we know about motive?

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

Utah Gov. Spencer Cox said family members told authorities that Robinson “had become more political 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.

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.

What do we know about Robinson?

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.

What has the fallout from the assassination been?

It prompted calls for greater civility in the country’s political discourse, especially on social media. But many people have made comments about the Kirk and the shooting that brought consequences, including firings.

MSNBC political analyst Matthew Dowd lost his job shortly after on-air comments about Kirk, one of the first of many figures to experience similar fallout.

Office Depot said Friday that it fired a worker at a Michigan store who was seen on video refusing to print flyers for a Kirk vigil and calling them “propaganda.”

Several Delta Air Lines employees were also suspended after social media posts that “went well beyond healthy, respectful debate,” CEO Ed Bastian said in a message to the company.

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.

Memorial to be held in Arizona

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.”

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 Sept. 17.