Beyond the parking dispute, police didn't comment further on the motivation or details of the crime, but a Muslim civil rights and advocacy organisation asked authorities to address speculation - much of it on social media - about possible anti-Muslim bias.
The three victims were Muslim, a friend said.
Craig Stephen Hicks, 46, was charged with three counts of first-degree murder in yesterday's shooting of Deah Shaddy Barakat, 23, Yusor Mohammad, 21, and Razan Mohammad Abu-Salha, 19.
Barakat and Mohammad were married, and Abu-Salha was Mohammad's sister.
Hicks appeared briefly in court this morning. He spoke only to answer that he understood the charges and to confirm an indigency affidavit. District Judge Marcia Morey said he would be appointed a public defender and held without bond until a March 4 hearing.
Police said Hicks was cooperating with the investigation and that their preliminary investigation showed that the parking dispute was the motive.
But outrage spread among American Muslims who viewed the homicides as an outgrowth of anti-Muslim opinions in the US Many posted social media updates with the Twitter hashtags #MuslimLivesMatter and #CallItTerrorism
"Based on the brutal nature of this crime ... the religious attire of two of the victims, and the rising anti-Muslim rhetoric in American society, we urge state and federal law enforcement authorities to quickly address speculation of a possible bias motive in this case," Nihad Awad, of the Council on American-Islamic Relations, said in a statement.
In an email, Chapel Hill police Chief Chris Blue said, "We understand the concerns about the possibility that this was hate-motivated, and we will exhaust every lead to determine if that is the case."
Durham district attorney Roger Echols said he couldn't discuss a motive. Asked whether Hicks could be charged with a hate crime, he said the facts of the case were still under investigation.
A spokeswoman for the US attorney's office in North Carolina that encompasses Chapel Hill didn't immediately return messages seeking comment about whether federal prosecutors were involved in the investigation or looking into a possible hate crime.
Gerod King of the Bureau of Alcohol, Tobacco, Firearms and Explosives said agents were in touch with the US attorney's office and that investigators hadn't ruled out a hate crime.
Abdullah Antepli, director of Muslim affairs at nearby Duke University, issued a statement calling for people not to jump to conclusions over the motive for the killings.
At UNC, Barakat was a second-year dental student, and Yusor was scheduled to begin dental studies in the fall.
Both had graduated from North Carolina State University, school spokesman Mick Kulikowski said. Barakat graduated with a business administration degree in the spring of 2013. Mohammad graduated in December with a biological sciences degree.
Abu-Salha was a second-year design major who had started classes last fall, Kulikowski said.
Muneeb Mustafa, 23, attended the same Raleigh mosque as Barakat.
"He was a completely genuine guy. Loving, caring, friendly, smart," Mustafa said. "He was an ideal human being. He was a role model."
Mustafa said they last saw each other about a month ago, playing in a basketball tournament staged by the Muslim Student Association at UNC, Mustafa said. Barakat, his wife of less than two months and his sister were all Muslim, Mustafa said.
Barakat's family was from Syria, and he was raising money to help refugees of the country's civil war, Mustafa said. Mohammad traveled to Turkey last summer to help treat dental problems in Syrian refugees in that country, Mustafa said.
The neighbourhood where they were found -- about three miles east of campus -- consists mostly of apartments and condominiums rented by students. Neighbours there said this morning that never before seen police or had crime problems.
Neighbour Samantha Maness said suspect Hicks "complained about noise and parking. So I wasn't extremely surprised" when he was charged.
"Anytime that I saw him or saw interaction with him or friends or anyone in the parking lot or myself, he was angry," she said. "He was very angry, anytime I saw him."
