Updated

A man accused in the shooting death of a transit guard in front of two women in downtown Denver is set to appear in court Thursday as police look for a motive for the apparent provoked attack.

Joshua Cummings, 37, was arrested shortly after Tuesday night's shooting near Union Station, a hub for buses and trains, and the city's pedestrian mall. Security camera footage helped police quickly find and arrest the suspected gunman.

The armed officer, Scott Von Lanken of Loveland, was wearing a dark blue uniform similar to those worn by police. In case he was targeted because he was believed to be a police officer, police Chief Robert White said officers have been warned to remain vigilant.

According to police, Von Lanken was trying to help two women who were afraid they had missed the last light rail train when one of them said she saw a man with a swollen face and "weird looking eyes" walk up to the officer and say something to the effect of "Do what you are told" before she heard a gunshot. He ran away but police found Cummings hiding on the patio of a nearby loft apartment building with a 9mm handgun.

Cummings, who has ties to a variety of cities in Texas, most recently Austin, was charged with a misdemeanor over five years ago out of state, police Commander Barb Archer said. It's not clear if he has a lawyer yet.

Gary Kim, the manager of the Holiday Motel in the Denver suburb of Englewood, said Cummings had been staying there for about three weeks.

Cummings previously stayed for about a month at the $365-a-week motel before leaving in late November and then returned in early January.

"He was one of my favorite tenants. I enjoyed seeing him," Kim said.

The motel manager said he didn't know what Cummings did for a living, but he would often volunteer to help people pay their rent.

Kim added that Cummings "kinda looked like a hippy" and had a full beard. He stayed at the hotel with a woman and a child, and Kim said he never noticed anything out of the ordinary.

Von Lanken was a contracted security officer for the Denver area's Regional Transportation District employed by Allied Universal.

Shellie Von Lanken told KUSA-TV in Denver that her husband of 35 years worked at least 65 hours a week to support her and their 32-year-old twin daughters, one of whom is disabled.

"It was unbelievable that any human being could even work what he was working," she said. "He just worked his heart out. He would tell me, 'If I could keep working, I would get another job just so I could provide for my family.'"

She added that if her husband were still alive, he would tell her and their daughters to forgive the shooter.

Soon after the area of the shooting reopened Wednesday morning, a group of motorcycle officers taped a blue sign along with flowers on a pole at the scene of the shooting offering their prayers as people walked by on their way to work.