Harris County (Texas) Sheriff Adrian Garcia on Monday calls for information leading to arrests in the January 2014 slayings of a Chinese family of four. Behind him from left are: Houston Chinese Alliance members Steve Pei, Howard Xu, Sun Yingying and Texas State Representative Gene Wu. May Zhou / China Daily

It has been more than a year since the killing of a Chinese family of four in their suburban Houston home, with no arrests made in the case.

The Houston Chinese Alliance (HCA) and Crime Stoppers announced Monday that an extra $5,000 was added to a reward in the case, bringing it to $75,000. The reward money was raised by the HCA.

Sun Maoye, 50, his wife, Xie Mei, 49, and their two young sons, Timothy Xie Sun, 9, and Titus Xiao Sun, 7, were found slain in their home on Jan 30, 2014. The possible date of death was estimated to be between Jan 24 and Jan 25.

According to police reports, all were shot once in the head and each was found in a different room in the house in northwestern Harris County.

Harris County Sheriff Adrian Garcia asked the community on Monday to have confidence and patience: "This is a complicated case. The last thing we want is to rush the investigation. Ultimately, we want justice and a conviction.

"The volume of evidence collected is incredible, and unfortunately, this is not the only murder case we have," Garcia said. "I'm asking you not to look at this case in its singularity; there are other violent crimes. We are still waiting for all results to come back from the Institute of Forensic Sciences," Garcia said.

Garcia said the investigators interviewed many people. He said there are many theories on what happened, but it does not help to speculate openly about the case.

Other than the fact that a gun was involved in the killings and that the case appears unrelated to others, Garcia declined to elaborate on any working theories, number of suspects, motives or any progress.

The Chinese community has been frustrated over the lack of progress in the case, said Sun Yingying, president of the HCA. The frustration is compounded by the fact that police are disclosing little information.

"Sheriff Garcia called for the perpetrator(s) to come forward to confess," Sun said. "I think this is unlikely to happen, therefore meaningless. We hope the police will step up the investigation. We can't be part of the investigation; we can only express our opinion on behalf of the community."

Sun also said that the HCA will get an update every two months from the sheriff's office.

Steve Pei, a professor at the University of Houston and a member of the HCA, said that the police probably got quite a bit of evidence to work with at first, but none led to any clear leads.

"However, we want the community to know that the investigation is still active," Pei said.

Howard Xu, HCA vice-president, said that many people shared similar backgrounds and lifestyles to the Sun family. The father was an engineer, and the children went to the local elementary school.

"We feel threatened; the community is disappointed due to the lack of progress," Xu said. "We urge the community to ask people with information to contact Crime Stoppers or the case investigators."

Texas State Representative Gene Wu appealed to anyone with information to "come out and share with us. The law enforcement needs it, we need to catch the people who did this, to heal. Please don't be afraid. Please come out and share your information with us."

Anyone with information is asked to contact Crime Stoppers of Houston at 713-222-TIPS (8477). Anyone providing information that leads to the filing of felony charges or an arrest/arrests in the case could receive up to $75,000.

mayzhou@chinadailyusa.com