Salt Lake City police are building a profile of the troubled young man who went on a shooting rampage inside the Trolley Square mall, killing five people and wounding four others before dying in a hail of gunfire.

"We have tried to develop a profile of this young man and make some reason why he would do the acts that he did, and at this point we don't have any motive," Salt Lake City Police Chief Chris Burbank said Thursday. "But there's nothing to indicate this had to do with race, religion or any other reason."

FBI Special Agent Patrick Kiernan said they remain involved in the investigation of the mass murder.

"We are providing whatever assistance is needed," he said.

Asked if the FBI is using its profilers to help learn more about Talovic, Kiernan said he could not comment because of the ongoing investigation.

On Thursday, detectives were talking to more people who knew Sulejman Talovic, trying to figure out what triggered the 18-year-old's homicidal fury inside the Trolley Square mall. His family, co-workers and any possible friends he may have had are being questioned to glean some insight and piece together the young man's final days.

Salt Lake City police detective Jeff Bedard said they are leaving "no stone unturned."

"Finding the motive is a huge deal for us," Bedard said Thursday. "It's the only way the victims' families can have some closure is knowing any reason why he did this."

However, police concede that the most painful question — why — may never be answered.

"It's a possibility that that may never be known," Salt Lake City police detective Robin Snyder said.

It's a question that even Talovic's family wants answered, but nobody seems to know.

"Nobody, like you guys ..., I don't know. I don't have any idea," his father, Suljo Talovic, said Thursday.

Burbank said that police are trying to get a portrait of Talovic's life.

"What his entire life was like, what his family life was like, everything that he was involved in, in order to come up with answers," the chief said. "We just haven't had anything concrete that points to motive at this point."

The FBI said part of that investigation includes Talovic's juvenile criminal record.

While the shooting rampage has spawned questions and hate-laden comments on the Internet about Talovic's Muslim faith, Salt Lake police and the FBI have said they have no evidence to suggest that terrorism is involved.

Sulejman Omerovic, a Bosnian immigrant who works as a taxi driver, said he met with the Talovic family on Thursday. While speaking to Suljo, he said a passage from the Quran came up in their conversation.