Police in south-central Florida on Thursday said they haven't established a motive for the deadly mass shooting at an area bank a day earlier that has led to charges against a 21-year-old former trainee prison guard.

Zephen Xaver, 21, faces five counts of premeditated murder. Five women — four bank employees and a customer — were killed.

Sebring police Chief Karl Hoglund said at a news conference Thursday that the accused has no apparent connection to the women or the SunTrust Bank branch.

Hoglund said the gunman "overtook the bank by force. He then shot everyone in the bank."

The chief said some of the families don't want their names released, citing Florida's version of a victims' rights law, but he identified two of them — customer Cynthia Watson and bank employee Marisol Lopez. He said the community is mourning the loss of "our sisters, our mothers, our daughters and our co-workers."

'I have shot 5 people'

Investigators said Wednesday that Xaver called police from inside the branch, saying, "I have shot five people."

Hoglund said Thursday that Xaver would not let authorities into the branch after more than an hour of negotiations. Hoglund said that by the time a SWAT team breached the building, "unfortunately, all victims had succumbed to their injuries."

All five women were found lying face down in the bank's lobby with gunshots to the backs of their heads, according to a police affidavit. The affidavit says shell casings from a 9-mm handgun were scattered on the floor, and authorities found the accused in an office in the rear of the bank.

Law enforcement officers stand near a Florida Department of Law Enforcement vehicle Wednesday at the SunTrust Bank branch in Sebring where the shooting took place. The victims have yet to officially identified. (Chris O'Meara/Associated Press)

The bank sits between a hotel and a hair salon in a business district of U.S. 27. The four-lane highway passes through farming communities and small towns as it connects South Florida and central Florida. Sebring, with 10,000 residents, is known internationally for its annual 12 Hours of Sebring endurance auto race that draws world-class drivers.

Witness Stefan Roehrig earlier told WFLA in St. Petersburg that the SWAT team attached cables to the door handles but ended up pulling the handles off, so they drove the armoured vehicle into the bank. They then led Xaver out in handcuffs.

"The suspect, they slammed him pretty good I think and brought him out here," he told the TV station.

Florida Department of Corrections records show Xaver was hired as a trainee prison guard at Avon Park Correctional Institution on Nov. 2 and resigned Jan. 9. No disciplinary issues were reported. Xaver lived in a non-descript prefabricated home about six kilometres from the bank. No one answered the door Wednesday night after police finished searching the home

John Larose, who lives next door, said Xaver kept to himself, but he could hear him playing and yelling at video games in the middle of the night.

Spate of Fla. mass shootings

Xaver briefly was an online student of Salt Lake City-based Stevens-Henager College. A spokesperson for the college, Sherrie Martin, confirmed that Xaver was enrolled from September 2018 until December, when he withdrew.

Xaver is originally from Indiana and attended high school there.

A woman who identified herself as a former girlfriend of the suspect told an Indiana television station that he often thought about hurting people and has long been fascinated with death and guns.

Xaver "for some reason always hated people and wanted everybody to die," Alex Gerlach told WSBT-TV, shortly after Wednesday's shooting. "He got kicked out of school for having a dream that he killed everybody in his class, and he's been threatening this for so long, and he's been having dreams about it and everything.

"Every single person I've told has not taken it seriously, and it's very unfortunate that it had to come to this," Gerlach said.

Sebring Police Chief Karl Hoglund said Thursday some of the victims might remain anonymous, by request of their relatives. (Chris O'Meara/Associated Press)

Gerlach told the Washington Post that Xaver said he purchased a gun last week and "no one thought anything of it" because he had always liked guns. Public records and neighbours say Xaver and his mother moved to Sebring in the fall from Plymouth, Ind., a small city south of South Bend, home of the University of Notre Dame.

Gov. Ron DeSantis was in the region for an infrastructure tour and travelled to Sebring after the shooting. He said the Florida Department of Law Enforcement would assist Sebring police and the Highlands County sheriff's office.

"Obviously, this is an individual who needs to face very swift and exacting justice," DeSantis said of the suspect.

This was at least the fourth mass shooting in Florida with five or more dead in the last three years:

A gunman killed 49 at an Orlando nightclub in 2016.

5 died at the Fort Lauderdale airport in 2017.

17 died in February at Marjory Stoneman Douglas High School in a Fort Lauderdale suburb.

SunTrust chairman-CEO Bill Rogers released a statement saying the bank was "working with officials and dedicating ourselves to fully addressing the needs of all the individuals and families involved."

The bank's "entire team mourns this terrible loss," he said.