Here's what we know about the suspect.
Police originally identified Ajayi as an interested person on Thursday after having issued a search warrant in his home in the Fairpark neighborhood.
The chief of police in Salt Lake City, Mike Brown, said at the time that Ajayi had spoken to investigators but was not in police custody.
Ajayi's house is located five kilometers from the park, where Lueck was last seen by a lift – driver who gave her a trip from the airport tomorrow morning on June 17th.
Police said the investigation showed Ajayi and Lueck's phones were both in the park within one minute of each other.
Ajayi refused to know how Lueck looked, Brown said, but the investigators found several pictures of her on her phone.
A neighbor told CNN that Ajayi said he used part of the home as an Airbnb.
Reached for comment Thursday, a spokesman for Airbnb told CNN that the company was "quick inquiry."
He probably burned Lueck's personal stuff
Neighbors told police Ajayi used gasoline to burn something in his backyard on June 17 and 18, Brown said Friday.
Police searched the firewood and said they found "more charred items" that were in line with Lueck's personal items, Brown said.
They also found charred material destined to be female human tissues, he said, which matched Lueck's DNA profile.
He worked for the US Army, Dell and Goldman Sachs
According to his LinkedIn site, Ajayi is a former US Army IT specialist and recently worked for Dell and Goldman Sachs.
CNN has reached the US Army and Dell for comment.
His neighbor, Tom Camomile, told CNN prior to his arrest that Ajayi was a "smart guy" and a "computer geek."
"It's a little uncomfortable and disturbing" that Ajayi was associated with the case, chamomile said at the time.
"I think he is a man of high integrity," he said, "but you know no one."
"Surprises come up all the time."
CNN's Sara Weisfeldt, Scott McLean, Melissa Alonso and Chris Boyette contributed to this report.