Investigators who followed his cellphone discovered that 23-year-old Mackenzie Lueck and the man expected to be charged with her murder were both in the park, where she was last seen on June 17 within one minute of each other.
About that time, Lueck's phone stopped receiving data or location services, police said
Ayoola Ajayi, 31, was arrested Friday and is expected to be charged with aggravated murder. He also faces charges of aggravated kidnapping, prevention of justice and dismissal of a body, according to Salt Lake City police chief Mike Brown.
After Lueck disappeared, the suspect initially refused to know how she looked, Brown said. But several pictures of her were found on his phone, and the "digital footprint" has continued, even after the arrest, police said.
An Instagram account, confirmed by Lueck's sorority sister, belongs to the missing student followed by another user on or around Wednesday, CNN verified.
Brown confirmed that investigators look at the activity on the account.
"This is a digital forensic examination," he said. "This covers computers, mobile phones, IP addresses, URLs, text programs."
Legal research has also been discovered
But the study is not only limited to digital footprints.
Investigators also found forensic evidence after they sought Ajayi's home and property Wednesday, police said. As they said, his neighbors to the police said they saw him using gasoline to burn something in his backyard on June 1
Police said the search gave more evidence.
"A legal claim was made on the firewood area, which resulted in the finding of several charred items that were in accordance with the personalities of Mackenzie Lueck," Brown told reporters.
Police also discovered charred material that was determined to be female human tissue according to Lueck's DNA profile, he said. A mattress researcher has tried to find has been placed, police tweeted Friday night without providing additional information.
She stopped communicating about 3 am
Lueck texted her parents at. 1 on June 17, when she landed at Salt Lake City International Airport, police said. She was seen on airport surveillance that went through baggage requirements before taking Lyft to Hatch Park.
The lift driver said she didn't seem to be in distress, according to Salt Lake City police chief Tim Doubt.
On Friday, the police said that all communications with Lueck's phone ceased at about 10am. 3 in the morning – at the same time they said she left the park with the suspect.
Phone records showed that her last message was with the suspect, Brown said. Her family and friends didn't see or hear from her that morning. Her sister of sorrow told CNN affiliate KSL that Lueck had also missed exams.
"She's extremely dedicated," Ashley told the fine television station. "She would never miss her midterms or anything like that. She hasn't been home. She didn't show up to work or anything."
A suspect is arrested
After the suspect's arrest on Friday, Brown contacted his parents to tell them the news. They were "destroyed and disturbed by this news," he said.
"This is one of the hardest phone calls I've ever made, "he said.
The suspect lived about five miles from the park where Lueck was last seen.
According to his LinkedIn page, he is a former information technology specialist for the US Army and recently worked for Dell and Goldman Sachs. CNN has reached the US Army and Dell for comment.
CNN's Dakin Andone contributed to this report.