RALEIGH, N.C. — As thousands of mourners gathered to honor the three young Muslims gunned down this week, the father of two of the victims asked for a federal investigation into the shooting.

“I call upon the President of the United States, Barack Obama…please involve the FBI. Please investigate,” Mohammad Abu-Salha said during funeral services for his daughters and son-in-law. He added: “This has hate crime written all over it.”

The FBI said Thursday evening it had opened “a parallel preliminary inquiry to determine whether or not any federal laws were violated.”

While police have said that the initial investigation suggests the shooting centered on a long-running argument over parking, Abu-Salha said the incident “was not about a parking spot.”

The community here has struggled to make sense of what happened at a housing complex near the University of North Carolina and figure out why three people — Deah Barakat, 23; his wife of a little more than six weeks, Yusor Mohammad Abu-Salha, 21; and her sister, Razan, 19 — were shot and killed. Police have charged Craig Hicks, 46, with the three killings, which drew worldwide attention amid fears that they were targeted for their religion.

Police in Chapel Hill, who are investigating the shooting, said that their initial work suggested that the shooting was motivated by a parking issue. This possible explanation fell short for many, and as news of the killings reverberated around the world, sorrow over the shooting was followed by disbelief that something as mundane as parking spaces could explain why three people were killed.

In particular, attention turned to the social media postings of Hicks, the middle-aged neighbor who turned himself in for the shootings early Wednesday morning.

Hicks described himself as an atheist on his Facebook page and had frequently criticized religion in his posts, sharing images and links decrying religious groups and beliefs. These postings were cited by Muslim civil rights advocates and others who urged police to explore the possibility of religious bias.

Craig Stephen Hicks, 46, was charged with murder in the killings of three young Muslim neighbors in what police have said was probably a dispute over parking. The victims' families still demand an investigation into what they say could be a hate crime. (Reuters)

“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,” Chris Blue, the Chapel Hill police chief, said in a statement Wednesday.

Authorities were called to the housing complex on Tuesday afternoon following a report of gunshots. A woman called 911 to say she heard between five and 10 shots as well as “kids screaming,” according to a recording of the call. All three victims were pronounced dead at the scene.

Police had not released any new information on the investigation on Thursday. The FBI is assisting the Chapel Hill police force in the investigation, saying that the department had asked for help processing evidence. Ripley Rand, U.S. attorney for the middle district of North Carolina, said the shooting appeared to be an isolated incident and not part of a targeted campaign against Muslims. He also said his office was monitoring the investigation.

Hicks’s wife held a news conference to insist that the shooting was only based on “the long-standing parking disputes that my husband had with the neighbors,” not religion or bigotry. She said he did not have a job and was studying to become a paralegal.

On Thursday, an attorney for Karen Hicks said in an e-mail that she was seeking a divorce. The same attorney said Wednesday that the shooting highlighted the importance of improving access to mental health care, but refused to comment on whether Craig Hicks had a history of mental health issues.

Cynthia Hurley, Hicks’s ex-wife, who said they were divorced nearly two decades ago, said his favorite movie was “Falling Down.” That movie, released in 1993, starred Michael Douglas as a man who goes on a violent rampage.

“That always freaked me out,” she told the Associated Press. “He watched it incessantly. He thought it was hilarious. He had no compassion at all.”

Neighbors have described Hicks as being loud and aggressive, someone prone to confrontation and angry outbursts. This made him an outlier in a complex described by residents as quiet and friendly.

Barakat had talked several months ago about a neighbor with a holstered gun on his hip who had come to his house to complain about parking, said Ali Heydary, who was close friends with Barakat.

Amid questions regarding the motive and calls for a larger investigation, the family and friends of the victims gathered Thursday to mourn the lives lost this week.

A crowd flooded a soccer field on the campus of North Carolina State University, where Barakat and his wife had graduated and where Razan was a sophomore studying architecture. After the funeral service hosted by the Islamic Association of Raleigh, the three were taken to a nearby Islamic cemetery to be buried. The university planned a candlelight vigil for later in the evening.

“We’re not sad,” Mohammad Abu-Salha said during the service. “We have peace inside. We are not seeking petty revenge. Our children are much more valuable than any revenge.”

The mourners were gathered in front of a stage that had been erected for the service, surrounded by police, some on horseback, who patrolled the area.

“It’s very sad to see such a beautiful family ripped apart because some random person came and killed their children,” said Anza Abbas, 20, a senior at the University of North Carolina.

She didn’t know the three, but still wanted to come out to the service because she had heard about how they were “star, model people who set a standard.”

“They showed us you can become educated, be a good student, a good citizen and at the same time, you can be a good Muslim and a good Muslim American,” she said.

Another woman who came to the service said she was there for solidarity. “This is our community, and our community got hit, so we want to be here together,” said the woman, who did not want to be identified.

Sullivan reported from Raleigh. Berman reported from Washington.

RELATED: Two universities in mourning after the shooting

[This post has been updated.]