A Cal State Fullerton employee has been taken into custody in the on-campus killing of a consultant who was found fatally stabbed in his car Monday.

Chuyen Vo, 51, was arrested at 10:16 p.m. Wednesday at his home in Huntington Beach for the slaying of 57-year-old Steven Shek Keung Chan, Fullerton Police Chief Robert Dunn said at a press conference Thursday afternoon.

Dunn said Chan and Vo were co-workers at the university and Vo allegedly “acted alone during the planning and commission of this murder.”

A motive for the killing is still unknown but police said that Chan was specifically targeted.

“In the coming days and weeks we will be working with the Orange County District Attorney’s Office to understand the motive behind this tragic killing and to pursue a successful prosecution of Mr. Vo,” Dunn said.

Officers were called to a parking lot near the College Park building about 8:30 a.m. Monday after a witness reported a “male down, bleeding from the head.”

“The witness did see what he described as an altercation,” Fullerton police Lt. Jon Radus previously told PEOPLE. “The altercation was in and around the car.”

Fullerton California Police

• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.

Officers found Chan inside his car with numerous stab wounds. He died at the scene.

Investigators found a backpack underneath Chan’s vehicle, containing zip ties, wigs, a knife and other disguise materials “consistent with a kidnapping attempt or plot.”

Radus said the backpack belonged to Vo.

At the Thursday press conference, Radus said the backpack belonged to Vo and it played an important role in catching the alleged killer.

“There were certain items in that backpack that were disturbing to say the least and it obviously did play a significant role in our investigation,” he said.

Chan was employed with the university as its director of budget and finance and student services for university extended education for almost 10 years. He retired in 2017.

Chan came back to work as a special consultant in early 2019, according to Cal State Fullerton President Fram Virjee.

“I did not have the honor of knowing Steven personally or working with him directly, but over the past few years, in providing a shoulder to lean on for those who were close to him, it is clear that he was beloved for his commitment to and passion for both Cal State Fullerton and our Titan Family,” Virjee wrote in a letter on the university’s website.

Vo is being held without bail.