Police on Friday sought two gunmen who opened fire inside a crowded coffee shop, killing one man and wounding six others, several critically, in a suspected gang-related revenge attack.

Sheriff Lee Baca said it appeared the masked gunmen were targeting a specific person.

"The manner in which it was done suggests it was a payback situation or a revenge situation," Baca said. "They had a specific person they were trying to shoot."

Sheriff's officials said it did not appear to be a robbery because the shooters opened fire immediately and did not demand money.

"The preliminary investigation would lead homicide detectives to believe this is gang-related," sheriff's spokesman Steve Whitmore said.

The shop was crowded with at least 40 people when the attack occurred late Thursday, but deputies were having a hard time finding witnesses.

"We know people saw something," Whitmore said. "And we need them to come forward and help us solve this crime."

The Coffee House cafe is located in a strip mall along a busy street about 20 miles east of Los Angeles. A Chinese bakery, foot massage parlor and Vietnamese restaurant are nearby.

An initial report by authorities said two people had died in the attack, but Whitmore said only one was dead. The victim's identity was not immediately released.

Two of the wounded people were taken to hospitals in critical condition, authorities said.

Four people who appeared to work at the cafe declined to speak to a reporter as they mopped up pools of blood and swept away blood-soaked playing cards and glass from a smashed table top.

Owners and customers at surrounding businesses were reluctant to discuss the attack. Some said they did not speak English.

One person, who asked to remain anonymous because of fear of retaliation, said the shop was a popular nighttime hangout for young people, and police had been called there in the past.

The shop's surveillance cameras were not working properly and did not record the attack, San Gabriel police Sgt. Rene Hernandez said.

Responding officers who received a panic alarm call from the shop were flagged down by several people who had been shot, he said.

Continuous coverage at MyFOXLA.com