A man suspected of shooting and killing an armed RTD transit security officer late Tuesday night was captured on surveillance footage and identified by an eyewitness, according to court documents.

The man, identified by Denver police as 37-year-old Joshua Cummings, was arrested after officers discovered him hiding on a patio outside a condominium about two blocks from the scene of the shooting at 16th and Wynkoop streets near Union Station.

The Denver medical examiner’s office identified the victim as Scott Von Lanken, 56, of Loveland.

Von Lanken was a contract worker for RTD from Allied Universal. He was married to his wife Shellie for 35 years and together they have twin daughters who are 32 years old.

"He was such a wonderful father. He worked so hard to try to take care of his family," Shellie said. "It was unbelievable that any human being could even work what he was working. He worked about 65 hours a week. There were times in the last few years where it was even more than that, where he was working 75 to even 80 hours a week."

On of their daughters is disabled and Shellie says he worked hard to make sure he would always be able provide for her.

Scott Von Lanken
Scott Von Lanken

"He has always just worked so hard just to take care of them. The stress that he carried was tremendous on this," Shellie said. "He did it because he just loved his family so much."

Investigators were working Wednesday to determine what led up to the shooting.

According to an arrest warrant affidavit obtained by 9NEWS, two women approached Von Lanken just after 11 p.m. Tuesday to ask him whether they might be able to catch a light rail train. Just then, one of the women told police “she observed the suspect approach the victim from behind a place a gun near his neck.” The woman said “she heard the suspect say something to the effect of, ‘Do what you are told.’”

A moment later, the gunman fired, then ran off as the mortally wounded security officer crumpled to the ground.

Responding officers were searching the area when a security officer at a building at 1400 Wewatta St. told them there was surveillance video of the suspect leaving the area. After watching the video, the officers continued their search, locating the man about 11:50 p.m. on a patio of a complex at 1628 14th St.

They arrested Cummings there.

According court documents, Cummings had a loaded 9mm pistol with him when he was arrested. Officers found a live round in the gun’s chamber and seven more live rounds in the magazine, which holds eight rounds. That ammunition was the same brand as a single shell casing found at the shooting scene, according to the documents.

Angela Burrell, public relations manager for Allied Universal, issued a statement about the shooting:

“Allied Universal is devastated by the loss of our valued security professional, a dedicated six-year employee, who was shot in the line of duty last night while proudly performing his duties in downtown Denver. We offer our deepest condolences to his family, friends and loved ones. The company intends to make a contribution in honor of the family to show our unwavering support. We ask that you join with us in keeping our fallen comrade’s family in your thoughts and prayers.”

Denver Police Chief Robert White said local authorities had no prior contact with Cummings and that his only criminal history was a misdemeanor charge in another state.

“We’re not 100 percent sure what motivated this particular individual to shoot the victim,” White said.

White said investigators were trying to determine if the security officer was shot because of his dark blue uniform, which resembles the one worn by DPD.

Barb Archer, the commander of the Denver Police Department’s Major Crimes Division, called the attack “completely unprovoked.”

"I would like to know why he would do this," said Van Lanken's wife Shellie. "And if you could understand the pain that he caused, how somebody’s life could just be changed overnight, never take for granted, never, the people you love because you don’t’ know if you’re going to see them tomorrow. I know at the same time, my husband would tell us to forgive him."

Von Lanken died on the way to the hospital. He was one of 250 contract security officers employed by RTD.

Anyone who was in the area Tuesday night and may have seen something was asked to call Denver Police.

A memorial fund has been set up for Von Lanken. You can help his family here by making a donation in the name of Scott Von Lanken at the Rocky Mountain Law Enforcement Credit Union.