By Nora Naughton and Rebecca Davis O'Brien

INDIANAPOLIS -- A makeshift memorial sprung up and vigils were planned Saturday for the victims of the mass shooting that killed eight people, as law-enforcement officials continued to investigate the shooter's motives.

Brandon Hole, a 19-year-old former employee of FedEx Corp ., killed eight people and wounded several others before taking his own life at the company's ground facility here Thursday night, police said. Mr. Hole had been temporarily committed last year for mental-health problems, and the FBI also confiscated a gun from him last year, authorities said.

Late Friday, police released the names of those who died in the shooting: Matthew Alexander, 32 years old; Samaria Blackwell, 19; Amarjeet Kaur Johal, 66; Jasvinder Kaur, 50; Sardar Jaswinder Singh, 68; Amarjit Sekhon, 48; Karli Smith, 19; and John Weisert, 74.

Among those killed were at least four members of the Sikh community, according to the Sikh Coalition, a national advocacy group, and executive director Satjeet Kaur said the coalition is in touch with law-enforcement officials.

As with the shootings last month in Atlanta -- in which six of the eight victims were women of Asian descent -- the preponderance of Sikh victims in Thursday's shootings raised questions about whether the attack was motivated by ethnic or religious animus.

"We fully expect that authorities should and will conduct a full investigation -- including the possibility of bias as a factor," the coalition said in a statement.

"We are not ruling out any motive at this time," Paul Keenan, special agent in charge of the Federal Bureau of Investigation's Indianapolis office, said in a statement. The Indianapolis Metropolitan Police Department is leading the investigation, he said.

"The FBI continues to work with IMPD and other law enforcement partners to find a motive for this senseless act of violence, and will be meticulous and thorough in our investigation and devote as much time as needed to find answers for the victims' families," Mr. Keenan said.

At least three vigils were planned in the area Saturday, including one at 1 p.m. at Olivet Missionary Baptist and a candlelight vigil at 7 p.m. at Krannert Park.

K.P. Singh, a local designer and longtime member of the Sikh community in Indianapolis, is working with faith leaders to honor the victims of Thursday night's shooting at a service for the religion's highest holy day on Sunday. He would like a portion of the service, normally all in the Punjabi language, to be said in English and is hoping all victims' family members will join for a lunch after the service.

"This is normally a very joyous day for us, so this is adding a large shadow," Mr. Singh said. He said while the Sikh community is reeling from losing four of its own members, they also are grieving the loss of their co-workers and friends who also died in the shooting.

"I hope we can come together and start thinking about what steps we can take to keep all of our families, neighborhoods, schools and workplaces safe -- not a month or a year from now, but right now," he said.

The Sikh community has been growing in Indianapolis since the late 1990s, according to a history of the Sikh Satsang of Indianapolis posted on a website for Butler University, a private college located in Indianapolis. The local congregation has grown from 50 to more than 1,000 community members in the last decade, most of whom are from the Punjab region on the border of India and Pakistan, the website says.

Sikhism is a monotheistic religion founded in India in the 1400s. Because some Sikhs wear turbans they sometimes are confused with Muslims, and some Sikhs have been the targets for violence or harassment in the aftermath of the Sept. 11, 2001, attacks.

In 2012, a white supremacist attacked a Sikh temple in Oak Creek, Wis., killing six people and then himself. The incident is still raw among Sikhs in the US.

The attack was the fourth public mass shooting in the U.S. in which four or more people were killed this year, according to the Violence Project, a mass shooting database maintained by two university professors. When domestic violence and gang-related attacks are added, there have been a total of 11 shootings in which four or more people were killed this year, according to the Violence Project.

Saturday afternoon, on the other side of the city from the FedEx facility where the shooting took place, gun enthusiasts gathered at a gun and knife show at the Indiana State Fairgrounds. Some said they were concerned that Mr. Hole had a gun after being investigated previously.

"I absolutely believe in background checks, and they should be stronger, " said 24-year-old Christian Ritchey of Avon, Ind., as he walked out of the Indy 1500 Gun and Knife Show.

Another attendee Dr. Leo D'Ambrosio said he is more concerned about access to mental-health care.

"It's far more important to make mental-health care accessible to all Americans than any form of gun control," Dr. D'Ambrosio said.

Write to Nora Naughton at Nora.Naughton@wsj.com and Rebecca Davis O'Brien at Rebecca.OBrien@wsj.com

Corrections & Amplifications

This story was corrected at 10:55 p.m. ET to fix the misstated age and spelling of Jasvinder Kaur, 50 years old. This originally had Jaswinder Kaur, 64. In addition, the name of the event was misstated. It is The Indy 1500 Gun & Knife Show, not Indy 500 Gun and Knife Show.

(END) Dow Jones Newswires

04-17-21 1322ET