CHAPEL HILL, N.C. (AP) — The North Carolina man accused of killing three Muslim students in a dispute over parking spaces had earlier run-ins with his neighbors, sometimes while wearing a handgun on his hip.

Police were still trying to determine whether religious hatred played any role in the shootings, which shocked the bucolic college town of Chapel Hill and left many residents grappling to make sense of the crime.

Charged with three counts of first-degree murder is Craig Stephen Hicks, 46, who has described himself as a "gun toting" atheist. Neighbors said Wednesday he always seemed angry and confrontational. His ex-wife said he was obsessed with the shooting-rampage movie "Falling Down," and showed "no compassion at all" for other people.

His current wife, Karen Hicks, said her husband "champions the rights of others" and said the killings "had nothing do with religion or the victims' faith." She then issued another brief statement through her lawyer, saying she's divorcing him.

Officers were summoned by a neighbor who called 911 Tuesday evening to report hearing multiple gunshots and people screaming.

Found dead at the scene were Deah Shaddy Barakat, 23, his wife Yusor Mohammad, 21, and her sister Razan Mohammad Abu-Salha, 19. In a brief court appearance Wednesday, Hicks, who lived in the same apartment building as the victims, pleaded indigence and was appointed a public defender.

The women's father, Mohammad Abu-Salha, said police told him each was shot in the head inside the couple's apartment and that he, for one, is convinced it was a hate crime.

"The media here bombards the American citizen with Islamic, Islamic, Islamic terrorism and makes people here scared of us and hate us and want us out. So if somebody has any conflict with you, and they already hate you, you get a bullet in the head," said Abu-Salha, who is a psychiatrist.

The killings are fueling outrage among people who blame anti-Muslim rhetoric for hate crimes. A Muslim advocacy organization pressed authorities to investigate possible religious bias. Many posted social media updates with the hashtag #MuslimLivesMatter.

"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," Chapel Hill police Chief Chris Blue said in an email.

Chapel Hill Police asked the FBI for help in their probe, and Ripley Rand, the U.S. Attorney for the Middle District of North Carolina, said his office was monitoring the investigation. But Rand said the crime "appears at this point to have been an isolated incident."

About 2,000 people attended a candlelight vigil for the victims in the heart of UNC's campus Wednesday evening. Several people who knew them spoke about their selflessness as friends recounted kindnesses they had extended to others through the years.

Barakat and Mohammad were newlyweds who helped the homeless and raised money to help Syrian refugees in Turkey. They met while helping to run the Muslim Student Association at N.C. State before he began pursuing an advanced degree in dentistry at the University of North Carolina at Chapel Hill. Mohammad, who graduated in December, planned to join her husband in dentistry school in the fall.

Abu-Salha was visiting them Tuesday from Raleigh, where she was majoring in design at N.C. State.

"This was like the power couple of our community," said Ali Sajjad, 21, the association's current president.

Many of the condominiums in the complex are rented or owned by students and recent graduates at UNC, whose campus is about 3 miles away.

Hicks had less success: Unemployed and driving a 15-year-old car, his wife said he had been studying to become a paralegal.

A Second Amendment rights advocate with a concealed weapons permit, Hicks often complained about both Christians and Muslims on his Facebook page. "Some call me a gun toting Liberal, others call me an open-minded Conservative," Hicks wrote.

Imad Ahmad, who lived in the condo where his friends were killed until Barakat and Mohammed were married in December, said Hicks complained about once a month that the two men were parking in a visitor's space as well as their assigned spot.

"He would come over to the door, knock on the door and then have a gun on his hip saying, 'You guys need to not park here,'" said Ahmad, a graduate student in chemistry at UNC-Chapel Hill. "He did it again after they got married."

Both Hicks and his neighbors complained to the property managers, who apparently didn't intervene. "They told us to call the police if the guy came and harassed us again," Ahmad said.

"This man was frustrated day in and day out about not being able to park where he wanted to," said Karen Hicks' attorney, Robert Maitland.

The killings were "related to long-standing parking disputes my husband had with various neighbors regardless of their race, religion or creed," Karen Hicks said.

Police have not said how Hicks got inside the condominium, but on Wednesday afternoon there were no visible signs of damage to the couple's door, which was affixed with orange stickers warning of biohazardous material inside. A wooden placard bearing Arabic script that translates to "Thanks to God" hung over their doorbell.

A woman who lives near the scene described Hicks as short-tempered.

"Anytime that I saw him or saw interaction with him or friends or anyone in the parking lot or myself, he was angry," Samantha Maness said of Hicks. "He was very angry, anytime I saw him."

Hicks' ex-wife, Cynthia Hurley, said that before they divorced about 17 years ago, his favorite movie was "Falling Down," the 1993 Michael Douglas film about a divorced unemployed engineer who goes on a shooting rampage.

"That always freaked me out," Hurley said. "He watched it incessantly. He thought it was hilarious. He had no compassion at all," she said.

A probable cause hearing is scheduled for March 4. Police said Hicks was cooperating.

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Dalesio reported from Raleigh. Associated Press writers Allen G. Breed in Chapel Hill, Jonathan Drew in Durham and Eric Tucker in Washington contributed to this report.

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