At first glance, the dark tinted glass doors at SunTrust Bank hid the horror unfolding within.

But Victor Sparks, a 20-year Sebring, Fla., resident and bank regular, was determined to solve this puzzle. It was 12:30 p.m. on a weekday. It was not a holiday. Yet the bank doors were locked.

He shielded his eyes from the Florida sun and pressed his face to the glass again.

Inside, Sparks saw several people on the lobby floor, face down and side by side, he said. Behind them was a man, pacing back and forth.

Unnerved, the 75-year-old Sparks said he calmly turned and walked toward his van, where his wife sat waiting. She saw a strange look on his face. He heard gunshots.

What Sparks learned later, after calling 911 and finding safety across the street, was that he might have been the last person to see the people inside that bank alive. Authorities identified the pacing man as 21-year-old Zephen Xaver, armed with a 9mm handgun and protected by a bulletproof vest.

He terrorized the five women Sparks saw on the ground — four bank employees and a bank customer -- before shooting them from behind, police say, in their heads and backs.

“If I had been five minutes sooner than I was, I could have been inside rather than outside,” Sparks said. “That’s probably the part that’s rattled us the most.”

Xaver’s alleged rampage, which left five dead and led to his arrest on five murder charges, shocked the town of Sebring, a small community of 10,000 people in the heart of Florida. A day after the shooting, people there still have few answers.

At a news conference Thursday, Sebring Police Chief Karl Hoglund said investigators have found no “true motive” for the bloodshed. It does not appear as though Xaver had any connection to the SunTrust Bank or the women killed there Wednesday afternoon, Hoglund said. He called it a “random act” with “no specific targets.”

He said that the investigation is ongoing and that the crime scene remains active.

Visibly shaken and emotional, Hoglund offered information about the five women, all members of the small Sebring community of 10,000.

“Our community suffered a tremendous loss at the hands of a heinous criminal,” Hoglund said. “Zephen Allen Xaver knowingly and intentionally took the lives of five of our fellow community members — our sisters, our mothers, our daughters and our co-workers. Perhaps most unfortunate is that we now refer to them as victims of a senseless crime.”

Hoglund identified the bank customer as Cynthia Watson, 65, and he named just one of the bank employees, Marisol Lopez, 55. A third victim, 38-year-old Ana Piñon-Williams, was later identified by her brother-in-law, who spoke on behalf of the family before reporters and said she was a mother to seven children and “truly a light in this world.”

“There is no law that can change the human heart, but there is a God who can,” Tim William told reporters. “[Ana] accepted others where they were in life. Loving came easy for her. Loving her was easy. Living without her will be hard.”

Williams said his family rejected the idea that prayer was useless after shootings like this and that they would be turning to their faith.

The police chief said family members of the two other shooting victims did not want the names of their loved ones released. The police chief cited a Florida statute that he said grants family members that right.

The unnamed victims were 31 and 54 years old, authorities said.

Authorities had previously said the gunman fatally shot everyone inside the bank but later clarified that a fifth bank employee survived. That person, whose name was not released, was inside the building’s break room when the shooting began, and called police after escaping through a back door.

Xaver, who friends and family said grew up in northern Indiana before moving to Sebring last year, has been charged with five felony counts of murder. Earlier Thursday, a judge denied him bond during his first court appearance. Xaver was shackled and hung his head. He did not speak.

At the news conference Thursday, Hoglund presented a minute-by-minute timeline of the shooting and its aftermath. The suspect entered the bank at 12:30 p.m. with a 9mm handgun and immediately took over the branch by force, investigators said.

“He then shot everyone in the bank,” Hoglund said.

At 12:36, Xaver called 911 and told dispatchers that he had killed five people inside, that he was armed and that he was wearing a bulletproof vest, according to an arrest report. Dispatchers remained on the line with him as Highlands County Sheriff’s Office deputies, Sebring Police Department officers, crisis negotiators and a SWAT team descended on the bank.

The bank doors were locked.

Xaver told negotiators that he would not allow medical personnel to treat the victims. Hoglund said he eventually ordered the SWAT team to enter the bank at 1:54 p.m. Xaver had barricaded himself in a room inside, and authorities eventually persuaded him to surrender.

Two hours after the shooting began, Xaver was in police custody.

“Unfortunately,” Hoglund said, choking up, “all victims had succumbed to their injuries inside the bank.”

Authorities found all five lying face down on the lobby floor, shell casings scattered around their bodies, according to the arrest report.

Two people who know Xaver told The Washington Post early Thursday that the suspect had talked about killing before.

Alex Gerlach, who said she dated Xaver on and off for about three years, said she met him in a psychiatric hospital in 2013 in Plymouth, Ind., the area where Xaver grew up and attended high school. Gerlach provided a photo of herself with Xaver to WSBT, a station in South Bend, Ind. (Xaver’s parents did not immediately return calls or messages from The Post to confirm whether a mental illness had been diagnosed.)

“Since the time we met, he had this fascination with death,” she said. “It got worse as we broke up.

She said that he told her last week that he had purchased a gun — a handgun, from what she remembers — but that “no one thought anything of it” because he had always liked guns, she said. A friend of Gerlach’s who also knew Xaver, and who spoke to The Post on the condition of anonymity, said Xaver had once told her he wanted to join the military “because he wanted to kill people."

Both friends say they had been encouraging him to seek help for years.

Josh Xaver, who identified himself as the suspect’s father, told CNN late Wednesday that his son moved to Florida about a year ago. He said he is “heartbroken for the victims."

“He wasn’t raised to be like this,” he said. “He’s always been a good kid. He’s had his troubles, but he has never hurt anyone before.” CNN noted that he did not elaborate on what troubles his son had faced.

An Army spokesman, William J. Sharp, said Thursday evening that Xaver reported to initial entry training in March 2016, and was separated from the service that June before completing it. No additional information was immediately available about what happened, he said.

While living in Sebring, Xaver was hired in November as a correctional officer trainee at the Avon Park Correctional Institution, about 17 miles northeast of Sebring, the Florida Department of Corrections confirmed late Wednesday.

Xaver resigned from that job on Jan. 9, the department said.

“He had no discipline while employed with the department,” Corrections Department spokesman Patrick Manderfield said.

Representatives of SunTrust Bank did not answer questions and said they were “deeply saddened” by the shooting at the Sebring branch.

On Thursday evening, Florida government buildings lowered flags to half-staff, where they would remain until sunset February 1.

Mass violence in public places frequently occurs after attackers have alarmed the people around them, research has shown. Many attackers had made threats or suggested they harbored an intention for violence before the bloodshed occurred.

An FBI study examining dozens of shootings between 2000 and 2013 found that more than half the attackers had revealed their desire to carry out violence. Sometimes this was a threat to people they later targeted, but in other cases, it was a broader desire to hurt people.

Dan Lamothe contributed to this report.