(CNN)A Sikh group is asking the FBI to investigate the recent killing of a Sikh man whose body was found near a park in Tracy, California.
According to police, Parmjit Singh, 64, was stabbed and left to bleed to death Sunday night while taking a routine walk to Gretchen Talley Park.
The United Sikhs, a United Nations-affiliated humanitarian relief organization, asked for the federal investigation and suggested Singh's death was motivated by prejudice.
Singh's son-in-law Harnek Kang, 40, told CNN that Singh was "very loving" and a "very nice man" who immigrated three years ago from India, where he worked as a farmer.
Singh, who lived with Kang, leaves behind a wife, a son and a daughter, and three grandchildren, Kang said. "It's a very big loss for the family. He's so close to my heart."
A community mourns
On Wednesday night, dozens in the community attended a candlelight vigil held in honor of Singh at the same park where he died, said Kang. "All the community in Tracy -- they are supporting me so much," he said through his tears. "Only thing I can say is thank you to all my neighborhood and fellow Americans and Sikh community during this tragic time in my life."
On Tuesday, the Tracy Police Department released a video and requested the public's help in identifying a potential witness seen near the park around the time that officers discovered Singh.
"We take pride in our safe, close-knit community. This violence will not be tolerated and we are dedicating every available resource to ensuring that the person(s) responsible for the death of Mr. Singh is brought to justice," Tracy Mayor Robert Rickman said.
Kang believes local officers are working hard to discover who killed his father-in-law, but he said he would be grateful for additional FBI assistance.
Tracy police, who continue to investigate, have provided no further information since releasing the video on Tuesday. They have not yet discovered a motive for the homicide and they do not specifically refer to the incident as a hate crime.
In a recent tweet, the United Sikhs allege Singh's death was motivated by prejudice, while the Sikh Coalition, an advocacy organization, also suggest that hate had something to do with the crime.
Legal Director Amrith Kaur said in a statement that the Sikh Coalition is "concerned by the fact that this is the seventh attack on an elderly, turban-wearing Sikh man since 2011 in the central valley and northern California region."
Last month, a priest at a Hughson Sikh temple was assaulted just outside the city limits, CNN affiliate KCRA reported.
"As we look to learn more, we expect that local law enforcement will continue to investigate this case thoroughly, including the possibility that bias was a motivating factor in (Singh's) murder," said Kaur.
Though Sikhism is sometimes confused with Islam, it is an independent religion with its own prophets, scriptures, practices, ceremonies, and beliefs, according to the Sikh Coalition. Worldwide, Sikhism is the fifth largest religion, with more than 25 million followers. The Sikh American population is estimated at 500,000, with the largest numbers located in California, New York and New Jersey.
The most visible aspect of the Sikh identity is the turban, or dastar, which is mostly worn by men.
Despite religious differences, an Islamic organization has called for support on behalf of Singh.
"We stand in solidarity with the Sikh community amid this heinous attack. We urge witnesses to come forward and help get justice for Parmjit Singh and his family," said Basim Elkarra, executive director of the Sacramento Valley office of the Council on American-Islamic Relations.
Kang expressed not only his private grief but a wider message of unity against violence.
"This is supposed to not happen in this country," he said. "This is so awful and my message to the people is to be careful. Everyday things happen all around the country that are not the right things. Somehow we need to stop those things. We need to get together."