A man allegedly shot dead three Muslim students execution-style near to the University of North Carolina campus on Tuesday after posting anti-religious sentiments online.

Craig Stephen Hicks, 46, shot dentistry student Deah Shaddy Barakat, 23, his new wife Yusor Mohammad, 21, and her sister Razan Mohammad Abu-Salha, 19, in their heads over an ongoing parking dispute at their quiet condominium complex in Chapel Hill around 5pm, police said.

But the women's father, Dr. Mohammad Abu-Salha, said even though parking might have triggered the killings, Hicks had long targeted the family because of their religion and culture.

'It was execution style, a bullet in every head,' Abu-Salha told the News Observer. 'This was not a dispute over a parking space, this was a hate crime.

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In court: Craig Hicks, 46, is pictured as he enters the courtroom for his first appearance at the Durham County Detention Center on Wednesday - a day after he allegedly shot three young students to death

Cuffed: Hicks, who has been charges with three counts of first-degree murder and is being held without bond, shot the trio dead amid an ongoing parking dispute, according to preliminary investigations

'This man had picked on my daughter and her husband a couple of times before, and he talked with them with his gun in his belt. And they were uncomfortable with him, but they did not know he would go this far.'

Dr Abu-Salha, who has one other child, added that police told him Hicks shot the three inside their apartment.

Hicks, who is married, turned himself in 'without incident' after the killings and is currently being held in Durham County jail on three counts of first-degree murder.

On Wednesday morning, he kept his head down as he appeared in an orange jumpsuit at the Durham County Detention Center. He is being held without bond.

Police say that he is cooperating, and that their preliminary investigation showed that the parking dispute was the motive.

There have also been questions over whether Hicks' anti-religious stance - which he freely shared on social media - had also been a factor in the murders.

On a Facebook page in his name, Hicks shared a number of anti-religion posts. A banner about 'anti-theism' is prominent on his page.

Hicks posted a photo from United Atheists of America on February 8, which has the title 'why radical Christians and radical Muslims are so opposed to each others' influence when they agree about so many ideological issues'.

Gunned down: (From left) Deah Shaddy Barakat, 23, his wife Yusor Mohammad, 21, and her sister Razan Mohammad Abu-Salha, 19, were all shot dead near the University of North Carolina on Tuesday

Heartbreaking: Yusor shared this beautiful photo showing her dancing with her father at their wedding. On Wednesday, he said that he believes the trio were shot due to their religion and culture

The students were shot dead near the quiet area of Finley Forest complex, near Summerwalk Circle

People claiming to be relatives gathered at the scene on Tuesday evening asking who the victims were

On the page he is listed as married and having studied to become a paralegal at Durham Technical Community College. Records show his wife works at UNC Hospital.

Most of the pictures he has posted in recent months criticize a number of religions, including Christianity. Other recent pictures he has published include one of a loaded revolver.

In one post allegedly written by Hicks and shared by CNN, he wrote: 'When it comes to insults, your religion started this, not me. If your religion kept its big mouth shut, so would I.'

Craig Hicks has been charged with murdering the three Muslim students after handing himself in

Police were called to Summerwalk Circle after shots were heard at about 5.10pm on Tuesday.

When they arrived they found three people dead. They had been shot in the head, CNN reported.

According to their Facebook pages, Mr Barakat had married his wife just over a month ago and was a second year student at the dental school at the University of North Carolina.

The last picture on his Facebook page, posted on January 29, said he helped provide free dental supplies to 75 homeless people in downtown Durham.

The couple had organised an online fundraiser to get dental care to refugees from Syria, raising around $15,000 - but after news of their deaths, the total reached more than $23,000

Mr Barakat was due to travel to Turkey in the summer to treat children who have become refugees following the civil war.

Last month, he tweeted: 'It's so freaking sad to hear people saying we should 'kill Jews' or 'Kill Palestinians'. As if that's going to solve anything SMH [shaking my head].'

His sister-in-law Razan Mohammad Abu-Salha had been studying for a degree at North Carolina State University in Architecture and Environmental Design.

After their deaths, Barakat's brother Farris paid tribute to the trio on Facebook as he struggled to comprehend the killings.

Outspoken: A Facebook page in Hicks' name clearly displays anti-religious sentiments

Hicks, pictured in an image he shared to Facebook, identified himself as an atheist on social media

Last December, he shared this picture showing him and his 'better half' Karen during a trip to Disneyland

Armed: Two weeks ago he shared this image of his 'loaded 38 revolver, its holster and five extra rounds'

'It doesn't make sense,' he wrote, 'and for that I rely on the Most Wise. It hurts and for that I know that God will not burden me more than I can handle.

'I know my brother, his wife, and his sister in law are together as ultimate winners. This life was only ever a test and they have passed with flying colors...

I haven't even begun to fully comprehend what has happened. But I know those three have done so much we are all proud of Deah Barakat's brother

'I haven't even begun to fully comprehend what has happened. But I know for sure those three together have done so much we are all proud of. No reason to stop being proud now.'

He added: 'We live as Muslims to die as Muslims. May Allah enter them to the highest of paradise.'

Following news of the deaths a hashtag #MuslimLivesMatter started trending on Twitter.

Burcu Bozcurt wrote: 'Hate will not prevail. Three beautiful souls taken, but examples of their love & impact on others abounds. #MuslimLivesMatter #chapelhill'

And MohaNNad said: 'Remember them like this. Deah and Yusor had names, dreams and families. #MuslimLivesMatter.'

The couple are only thought to have been married for just a month and were fundraising for Syrian refugees

People posted pictures of the couple, newly married, on Twitter just hours after they were both murdered

Well-known atheist Richard Dawkins also condemned the killings on Twitter. He said: 'How could any decent person NOT condemn the vile murder of three young US Muslims in Chapel Hill?'

People called for action to be taken with some speculating that the attack could have been religiously motivated.

A Facebook tribute page has been set up for the victims, called 'Our Three Winners'. It says: 'Deah Barakat, Yusor Abu-Salha and Razan Abu-Salha have returned to their Lord. They have set an example in life and in death.'

It noted that funeral arrangements will be announced after they receive news from the medical examiner, who will carry out an investigation and release the bodies.

The shooting took place in the Finley Forest complex - a typically quiet area home to students.

Bethany Boring encountered police cars, crime scene tape and people upset in the street when she went to walk her dog.

She told WRAL: 'It's a very quiet community. It's a lot of graduate and professional students. You know, professional's families.'

People have posted tributes to the trio on Twitter, with the hashtag #MuslimLivesMatter following the deaths

People living near Summerwalk Circle said the area was usually very quiet with little or no crime reported

Daniel Waggoner who lives in the area added: 'I'm up late. I come home late and it's always quiet when I get here,' he said. 'So I mean yeah, it's surprising.'

A campus crime alert from the University of North Carolina at Chapel Hill was sent to students. The complex is located near campus.

About two hours after the shooting a group of young people arrived at the scene and sat on the pavement, apparently waiting for news of the names of the people who had been killed. Police later turned away people in tears, claiming to be relatives.

The Chapel Hill Police Department said in a statement there was 'reason to believe that there is no ongoing threat to the public'.

The school added in a statement: 'We are sensitive to the impact an incident of this nature has on campus and in the community.