Cell phone photos and a rideshare helped lead to man's arrest in the killing of MacKenzie Lueck

SALT LAKE CITY (KSTU) -- Cell phones and social media were at the heart of the investigation that led to an arrest in the killing of a University of Utah student who vanished nearly two weeks ago.

Investigators tracking her cell phone 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 a minute of one another.

That was around the 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, obstruction of justice and desecration of a body, according to Salt Lake City Police Chief Mike Brown.

Police find her pictures on his phone

After Lueck disappeared, the suspect originally denied knowing what she looked like, 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 that Lueck's sorority sister confirmed belongs to the missing student followed another user on or about Wednesday, CNN verified.

Brown confirmed that investigators are looking into the activity on the account.

“This is a digital forensic investigation,” he said. “This is covering computers, cell phones, IP addresses, URLs, texting apps.”

Forensic evidence is also discovered

But the investigation is not just limited to digital footprints.

Investigators also found forensic evidence after they searched Ajayi's home and property Wednesday, police said. As they did, his neighbors told police they saw him using gasoline to burn something in his backyard on June 17 and 18, Brown said.

Police said the search yielded multiple items of evidence.

“A forensic excavation of the burn area was conducted, which resulted in the finding of several charred items that were consistent with personal items of Mackenzie Lueck,” Brown told reporters.