Three teenagers have been arrested in Utah for allegedly fatally shooting a 21-year-old man during a robbery and leaving his body in a "remote desert area," police said.

The three teenage boys — ages 15, 17 and 17 — are in custody and charged in connection to the homicide of Alexzia "Alex" Franco, Taylorsville police said in a Facebook post.

Detectives were initially investigating the case as an alleged abduction that occurred March 17 in a Taylorsville neighborhood, police said in the social media post. The case took a turn when Franco's body was found with a single gunshot wound in a desert area in Utah County, according to Taylorsville police.

Before police found Franco, he was seen getting into a white Jeep Liberty on Sunday afternoon, the social media post said. With the public's help, police found the Jeep in Salt Lake County, and further investigation led to the arrests of two of the teenage boys, according to the post.

Taylorsville police announced the arrest of the third suspect, one of the 17-year-old boys, on Thursday, a second Facebook post said. Police believe there are no other outstanding suspects, according to the post.

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Alex Franco was shot during a robbery attempt, police say

Taylorsville police believe one of the boys shot Franco during a robbery attempt, according to the department's second Facebook post regarding the case.

The shooting happened near Franco's home, and a shot was fired almost immediately after he got into the Jeep, Taylorsville police Lt. Aaron Cheshire said Wednesday during a news conference. Police said video footage from the scene “clearly identified the sound reported by witnesses as a gunshot."

Franco knew at least one of the individuals in the Jeep and got into the vehicle willingly, Cheshire said.

The boys are in custody at the Salt Lake Valley Detention Center, police said.

'He's a good kid': Alex Franco's aunt speaks

Franco's family spoke to KTVX about the shooting before the teenage boys were found.

“You know, he has a whole family that loves him,” Franco's aunt Sherry Bennett said. “I feel so helpless.”

Bennett told the Utah-based TV station that Franco was supposed to come over to her house and stay for a bit, but he never showed up. She figured her nephew may have been busy, but then his girlfriend texted her that Franco was missing, according to KTVX.

Bennett described to KTVX how Franco was a "good kid" who she did not think was involved in anything that could have led to the shooting.

“He’s had his tough spots and stuff, but he’s a good kid,” Bennett said. “He walks in the room and everyone brightens up immediately, so it’s really hard to even think that somebody could be so mad to do this to him.”

Alex chose to use "he, him" pronouns, his aunt Krystyn Mace told USA TODAY.

An Ever Loved was created to help pay for Franco's funeral. So far, the fundraiser has received $8,720 in donations, which surpassed its $5,000 goal.

"We are truly amazed & eternally grateful for the outpour of love Alex is receiving through you all! For everyone reaching out & contributing their kind words, donations, & shares! People from different states who didn't even know Alex Franco, to every family member, friend, teacher, schoolmate, coworkers, family members bosses, & random people in stores or the airport that we're connecting with," Zoe Franco, Franco's aunt, said in a Facebook post. "It's so amazing y'all!"

Jonathan Limehouse covers breaking and trending news for USA TODAY. Reach him at [email protected]