Surveillance video of the 17-year-old boy accused of killing Haruka Weiser shows that he watched the Portland woman walk past him while he sat on a bike at the University of Texas, an Austin detective wrote in an affidavit released Friday.

Meechaiel Criner put the kickstand down, reached into the back of his pants and pulled out a "shiny rigid object" Sunday night before following the 18-year-old dance major, whose body was found two days later, according to the Travis County District Court record signed by Detective Anthony Nelson.

More than two hours later he walked back to his bike, with a slight limp, carrying a duffel bag that he did not have when he initially appeared on screen, Nelson wrote.

The details emerged as the case -- the first homicide on campus in 50 years -- captured national attention. The court document was filed Friday, the same day the city's police chief and university officials held a news conference about the arrest.

"We are very certain the subject ... in custody is the suspect responsible for the death of this beautiful young women," Austin Police Chief Art Acevedo said.

Sunday night

Weiser was a 2015 graduate of the Arts & Communications Magnet Academy, a grade 6-12 magnet school in Beaverton Oregon, and an accomplished dancer. She performed with the school's Dance West troupe, as well as The Portland Ballet and Oregon Symphony.

She was attending in the Austin university on a dance scholarship but also planned to pursue a medical career, her family has said.

Weiser was last heard from on Sunday, when she called her roommate Sylvia Feghali to say she was on her way home after a class around 9:30 p.m., Nelson said. A missing person report was filed with campus police after Weiser did not show up for a Monday morning class, Nelson said.

Her roommate and friends told police that Weiser had been wearing a black turtleneck, black stretch pants and brown Doc Martin shoes, and carrying a blue duffel bag containing her laptop computer, iPhone, a jacket and study materials, Nelson said.

University police began searching for Weiser on Tuesday morning. They went over the route she was known to walk and found her body, with obvious trauma, near the alumni center. Her blue duffel bag was missing.

As university police detectives began reviewing Sunday night's surveillance footage, they noticed an athletic man, about 6 feet tall with glasses, wearing a black jacket and gray pants. He was riding a bicycle and attempting to open the doors of a parked van near a liberal arts building.

He rode away from the van but returned at 9:38 p.m., when a woman dressed in black and looking at her phone comes into view, Nelson said. The man followed her across a bridge and onto a sidewalk that leads to the alumni center, beyond the camera's view, Nelson wrote.

The man isn't seen on camera again until 11:47 p.m., when he returns to his bike carrying a duffel bag and rides away.

The fire

After police released a portion of the video to the public on Thursday, an Austin Fire Department captain called investigators about a small blaze his crew extinguished inside an abandoned building not far from where the male with the bike was seen walking, Nelson said.

When firefighters responded to the blaze about 8:21 a.m. Monday, they found a 17-year-old homeless boy burning items, Nelson said. Officers at the scene identified Criner and, instead of arresting him for the fire, agreed to drive him to a homeless shelter. Criner had been carrying several bags and a backpack, Nelson said.

The car ride was recorded on video, and Nelson on Thursday noticed that Criner wore the same type of clothing as the man in the surveillance video. Criner showed images of the blue duffel bag taken from the police car camera to Feghali. The roommate in turn showed them to a student who was at the same class Weiser attended Sunday night, Nelson said. That student, Ginnifer Joe, immediately identified the bag, Nelson said.

Detectives returned to the fire scene and, as they rummaged through ashes, found a Doc Martin shoe and a burned notebook. A black jacket was found nearby that appeared to be the same as the one worn by the male in the video, Nelson said.

"We were able to detain him for tampering with evidence and questioned him regarding this incident," Acevedo told reporters Friday.

At the homeless shelter, detectives found "evidence that matched the same texture, age and appearance of an article" found near Weiser's body. Detectives also found a laptop with a sticker that mentioned Portland, Nelson said. Weiser's family confirmed that she had such a sticker on her computer.

Acevedo told ABC's "Good Morning America" that the location and timing of the teenager's appearance on campus "and a lot of things we'd rather not talk about" indicate Criner is responsible for Weiser's death. Authorities still have not disclosed how she died.

The police chief said he didn't have any details about the motive and continued to ask the public for information about the Criner's whereabouts in the days leading to the killing.

Who is Criner?

In the Dec. 17, 2014, edition of The Tiger Times, a publication from Texas High School in Texarkana, an interview with Criner during his sophomore year provides a glimpse into his upbringing.

Criner told staff writer Raga Justin that he came to live in the city with his grandmother because his mother did not want him or his siblings.

"(Child protective services) had to transfer me and my four siblings," Criner told The Times. "My grandmother offered to take care of me and my sisters."

Before moving in with his grandmother, Criner said that he had bounced from foster home to foster home throughout grade school. He said he was the victim of violence, claiming that a foster parent threw him to the ground and injured his back. In another home, he said that he had been locked in a bathroom.

He said he was bullied in elementary school for his clothes and thick "African-like accent."

"I would come home crying almost every day," he said. "It was because of my accent, you see. People couldn't understand me."

Mary Wadley, his grandmother, told KSLA-TV in Texarkana that Criner went missing from her home in August.

"It's shocking because I've been looking for him," Wadley says in an interview posted by KEYE in Austin.

"He was a good person," Wadley said. "He was a sweet person. He was easy to get along (with) until you made him mad, he snapped, his temper. He snapped real fast."

Criner was receiving psychiatric help and taking medication, she said. She didn't say why he chose to leave Texarkana, but indicated that he was allowed to because of his age.

Criner told The Times he didn't know what his future held, but that he wanted to accomplish one thing.

"Every day, I feel people think I'm not capable of much," Criner said. "What I want to leave behind is my name. I want them to know who Meechaiel Criner is."

-- Tony Hernandez

thernandez@oregonian.com

503-294-5928

@tonyhreports

The Associated Press contributed to this report.