North Carolina police on Saturday released two ATM surveillance pictures of a person of interest in the case of a slain university student, which they said appeared to be a random killing.

Chapel Hill Police Chief Brian Curran, speaking at a news conference, described the pictures as "our biggest break so far" in the investigation into the death of Unversity of North Carolina student body president Eve Carson.

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Police have yet to identify the person in the photos, who apparently used an ATM card belonging to Carson, a senior who was shot to death early Wednesday on a city street not far from campus.

Curran said police have circulated the pictures with police departments in North Carolina, hoping their officers can help identify the suspect. The ATM photos show a young man in a baseball cap and hooded sweat shirt driving a sport utility vehicle that may be Carson's Toyota Highlander, Curran said.

Police also released a photo of a baseball cap the suspect appears to be wearing in both of the surveillance pictures. Curran declined to say when the pictures were taken.

Carson was last seen around 1:30 a.m. Wednesday, when she stayed behind at home to study while her roommates went out for the night. She was known to work late at her campus office, and Curran has said Saturday that "she may have mentioned something about needing to print off papers later that night."

But Curran has said police don't have any evidence that she made it to her office. There were no signs of forced entry to her home and police said they are not aware of anyone who might have been angry with Carson. There are no indications she had been sexually assaulted.

"She was studying at the house when her roommates last saw her," he said.

Police found Carson's body shortly after 5 a.m. Wednesday, after two callers to 911 reported hearing several gun shots. One of the callers also heard a woman scream as the shots were fired.

The UNC Board of Trustees is offering a $25,000 reward for information leading to an arrest in Carson's death. Anyone with tips should call Crime Stoppers at 919-942-7515.

Police on Friday began circulating the photos among state and federal law enforcement officials and made them public on Saturday, following the news conference.

Curran said police were pursuing several leads, putting together a timeline of calls made on Carson's phone and continuing to investigate a car believed to belong to the slain student. The car was found ticketed in a no-parking zone.

Curran encouraged anyone who might have seen the blue 2005 Toyota Highlander with Georgia plate AIV 6690 between 1:30 a.m. Wednesday and midday Thursday to contact police.

"We're now asking for any information the public can provide," he said.

Detectives said Carson was killed by a shot from a handgun to her right temple, and until late Friday appeared to have few solid leads.

Carson's death struck hard at North Carolina, where she was prestigious Morehead-Cain Scholar and leader who invited all incoming students to stop by her office for a chat. Her death led to a pair of memorial services on Thursday, attended by thousands, and a third is likely after classes resume following next week's spring break.

"It's just a huge blow. It's a blow against everything we assume about ourselves, about being a peaceful, safe place where kids come," University Chancellor James Moeser said. "She was a joyful person. She loved this place. She loved being here."

While in college, Carson studied abroad in Cuba and spent time working and volunteering in Ecuador, Egypt and Ghana.

She was involved in campus programs for hunger relief, among many other activities, and was featured on the Morehead-Cain Web site that described her experiences working in Ecuador. "One of the most important lessons I learned ... is that poverty is not a pitiable thing," she said. "In Chillanes, I saw a respect for poverty and a respect for a non-material way of life."

A pre-med student who majored in political science and biology, she was thinking lately about whether to instead accept an offer to work in New York for a business consulting firm.

"I could see Eve balancing a career as a professional, probably in the not for profit sector, but also being a wife and a mother because she was such a loving person," Moeser said. "The whole package. I get choked up thinking about it."

FOXNews.com's Heather Scroope and The Associated Press contributed to this report.