A 36-year-old Sikh man was shot dead by a masked gunman during an armed robbery at a convenience store in the US.

Amanjeet Singh Toor was shot dead early Monday during the robbery at the store in Arizona where he worked.

The assailant then chased the other employees out of the store before returning to grab a bag, police added.

The police, along with Toor's family are seeking the public's help to find the attacker. The shooter has been described wearing a dark hooded sweatshirt, face mask and red gloves.

Toor had immigrated from India six years ago along with his wife Kamaldeep Kaur. She had recently joined him in Phoenix from India, a report in AZCentral, an Arizona news site, said.

"This was a very hard loss for us. He was a role model for most of us," Toor's cousin Micky Gill said on Thursday at Phoenix police headquarters.

About 2,500-3,000 Sikh families live in the Phoenix metro area.

The incident again raised concerns over the safety of Sikh-Americans who have been targeted, in the years since the 9/11 attacks, in a slew of hate crimes because of their articles of faith, the beard and turban.

Rana Singh Sodhi, a Sikh and community activist, spoke on behalf of Toor's family, calling for the community to come together to find the perpetrator.

"He handed over the money, but was still shot. It begs the question (of racism)," Sodhi said in the report.

"We are new immigrants in this area, but we request the community come out and help get this person behind bars," he said.

Sodhi's brother was killed in a hate crime in Mesa just four days after the September 11, 2001, terror attack on the World Trade Center.

"Fifteen years later and we are still not treated right," Sodhi said.

"They come into our stores, give us the finger and shout, 'Go back to your country. This is a common thing for us.

Any terrorist attack that happens, we get affected every year.

Our lives have not been the same since 9/11," Sodhi said.