A gunman who had posted anti-religious messages on social media was charged with killing three Muslim students near the University of North Carolina in what police said on Wednesday was an ongoing dispute over parking.

Craig Stephen Hicks, 46, of Chapel Hill, was arrested and charged with three counts of first-degree murder, the Chapel Hill Police Department said in a statement. He was being held at Durham County Jail.

Muslim activists demanded that authorities investigate Hicks for possible hate crimes in the killings late on Tuesday of the three students who were all involved in humanitarian aid programs.

“Our preliminary investigation indicates that the crime was motivated by an ongoing neighbour dispute over parking,” police said in a statement. “Hicks is cooperating with investigators and more information may be released at a later time.”

Chapel Hill Police Chief Chris Blue said in a statement: “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.”

On Facebook, Hicks’ profile picture reads “Atheists for Equality” and he frequently posted quotes critical of religion. On Jan. 20 he posted a photo of a .38-caliber revolver that he said was loaded and belonged to him.

“Yes, that is 1 pound 5.1 ounces for my loaded 38 revolver, its holster, and five extra rounds in a speedloader,” the post said.

The victims in the shooting are Deah Shaddy Barakat, 23; his wife Yusor Mohammad, 21, and her sister, Razan Mohammad Abu-Salha, 19.

Barakat was a second-year dental student at the University of North Carolina. He and Mohammad were recently married, according to postings on a Facebook memorial page for the victims, and she was planning on starting dentistry school at UNC in the next school year.

Abu-Salha was a sophomore at nearby North Carolina State University, where her sister and brother-in-law were both alumni.

Anti-Religious Statements Cited

A spokesman for the Council on American-Islamic Relations (CAIR) told Reuters the three were Muslim.

“Based on the brutal nature of this crime, the past anti-religion statements of the alleged perpetrator, 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,” said CAIR National Executive Director Nihad Awad.

The shooting sparked the hashtag #MuslimLivesMatter on social media, with posters also questioning what role the students’ faith may have played in the incident.

A Facebook page titled “Our Three Winners” was created to honour the victims, and a vigil was planned near the university’s Chapel Hill campus for Wednesday night.

Officers responded to a report of gunshots at 5:11pm local time (2211 GMT) and found the three victims, who were all pronounced dead at the scene, police said.