CHAPEL HILL: Thousands of people gathered Wednesday in Chapel Hill to mourn three Muslim students killed by an anti-religion gunman who shot them in the head, rocking the tight-knit university town.

Friends and family poured onto the University of North Carolina campus to remember Deah Shaddy Barakat, 23, his new wife Yusor Mohammad, 21 and her 19-year-old sister Razan Mohammad Abu-Salha.

The three were allegedly killed by neighbour Craig Stephen Hicks, 46, whose Facebook page espoused his anti-religious views.

The murders are being investigated by Chapel Hill police as a hate crime, and sparked outrage among Muslims worldwide. Craig is charged with three counts of first degree murder, which carries a minimum sentence of death or life in prison without parole.

The killing rattled the university town, and thousands braved cold temperatures for a candlelit vigil.

“We lost three great citizens of this world and of this country. But I think they've inspired thousands,” Farris Barakat, Deah's brother said before a tearful crowd.

He remembered his younger brother, a UNC dentistry student, as passionate about sports, his profession and the odd Chris Rock joke, as photos of the slain students flashed on a large screen. But he urged restraint and said the murder should not provoke further violence.

“Do not fight fire with fire... it is quite possible that this was an act based off of evil and a scared ignorant man, do not let ignorance propagate in your life, do not reply ignorance with ignorance,” he said.

Barakat and Mohammad were married in late December, and the new bride was set to start dental school in August. Her sister had attended the nearby North Carolina State University. Mohammad's bridesmaids remembered her plans to run a marathon, her commitment to meditation and the mosque and her love for breakfast cereal. They recalled her as a kind person.

“To speak about Yosur she was one of the most innocent, most kind human beings I have ever met in my entire life. I cannot even imagine as to why this would happen to her, and the same goes for Razan,” said Omar Abdul-Baki, president of UNC dentistry school student body, speaking before a line of dental students in white jackets.

Barakat, the son of Syrian immigrants, was remembered for his community work, offering free dental work to the needy and for raising money for a planned trip to Turkey to help Syrian refugees.

Childhood friend Abdul Salem said the crowds at the vigil were a testament to the impact that all three had.

He remembered Barakat as “always smiling, always positive and I don't mean that lightly. Obviously when tragedy hits people tend to remember the best things. But I challenge anyone to remember anything other than that about them,” speaking after the vigil, surrounded by hugging and crying mourners.

"It's an opportunity for people to stop and remember not just the positive things, to remember them and not remember them only because of this tragedy."

Chapel Hill Mayor Mark Kleinschmidt called the three “exemplars of the community” and vowed that justice would be served.

“Whatever ridiculous, unthinkable thoughts inspired this action, he is done,” he said

Craig Kleinschmidt vowed to move on from the tragedy and said the community would rebuild.

“Losing them this early in life is just, it's just unspeakably tragic."

A funeral is scheduled for all three Thursday afternoon at the Islamic Association in neighbouring Raleigh.