A Monroe Marine’s sister said her family is “living in a nightmare” as news spreads around the world linking the man to a video of what appears to be a U.S. Marine throwing a puppy off a desert cliff.

Death threats and graphic descriptions of physical violence continue to be directed at the Marine and his extended family as their personal information is being spread on the Internet.

That information on Tuesday continued to be posted on various blogs, social networking sites and online forums.

“They are getting angry about this puppy and the loss of this puppy, if this is real,” the sister said in an interview with KIRO (710-AM) radio talk-show host Dori Monson. “On the same hand, they are also threatening human beings’ lives. They are putting this puppy’s life above human beings.”

Local law enforcement and national animal rights groups are calling for people to express their emotions in a civil way. The U.S. Marine Corps is investigating, attempting to determine whether the event shown in the video — dramatic though it is — is authentic.

“Obviously, the video is extremely disturbing,” said Inga Gibson, Washington state director for the Humane Society of the United States. “We will not condone any threats or violent behavior. We are solely seeking an investigation.”

Thousands of people have contacted the national group about the video, which started getting attention on Monday, Gibson said.

Marine Corps investigators have yet to identify who appears in the video or where or how it was created. They haven’t yet concluded whether the video is authentic or a hoax.

In either case, Marine Corps officials do not like what they have seen, condemning the video in a statement released Monday.

The Marine from Monroe is stationed at Marine Corps Base Hawaii, and that is where the investigation is being conducted. The Herald is not identifying the Monroe man because of many questions surrounding the video.

“I understand people’s outrage,” Maj. Chris Perrine, a spokesman at the Kaneohe Bay Marine Corps base in Hawaii, told The Honolulu Advertiser on Tuesday. The Monroe Marine is at the base. “I think every Marine is outraged by the video, and what I would do is encourage people to support our Constitutional process and treat people as innocent till proven guilty and let the process run its course.”

The blurry 17-second video makes it difficult to tell whether the puppy is a toy or real. It dangles motionless as someone dressed as a Marine holds it by the scruff of the neck. The man throws it into a gully and shrugs at the camera.

The video has gone viral, spreading through e-mails and multiple Web postings. It is making international headlines, appearing in news stories in Australia and Germany and on CNN, Fox News, MSNBC and Wired magazine’s Web site.

The video already has been viewed more than 145,000 times on YouTube.com, where copies of the video are posted as quickly as they are taken down.

The site also features dozens more video blogs offering individuals’ opinions to the video.

Many sites keep posting the Monroe family’s personal information, which exposes them to harassment and verbal abuse.

A deputy from the Snohomish County Sheriff’s Office visited the Monroe family on Monday, said Rebecca Hover, a sheriff’s spokeswoman.

The family has disconnected their phones following threatening calls.

“With the phones out, they shouldn’t have any more problems with harassing calls, so now we want to make sure they are safe in their home,” Hover said.

An investigation into any threats would be started if the family chooses to report them, Hover said.

“What it says for them is when they are so passionate about a single dog’s life, yet they are willing to — they say they are — willing to kill the entire family over something like this,” the sister of the Marine from Monroe told KIRO. Her brother has served his country in Afghanistan and Iraq and “none of them take that into account,” she said. “They just want to jump on him and immediately call him a mental maniac.”

The sister did not return a phone call from The Herald seeking comment.

In cyberspace, some posters were calling for restraint, saying that threatening the man’s family is wrong and pointless.

“Some of the comments made toward the innocent family members of this Marine by certain Web site owners, bloggers and their responders — and their actions — have bordered on the criminal in my opinion, and many have very frankly crossed well over that line. I saw one vile post advocating a sexual assault on this Marine’s mother,” wrote one poster, IrishRose, on the conservative commentator Michelle Malkin’s Web site.

“I am not defending what he did,” wrote toothygrim on Digg, “because it is inexcusable. … but do we have any proof that the guy in the video is actually the guy whose name and address people are posting? I personally have no idea, but it would be really sad if someone else is getting all the hate mail and threatening phone calls and it wasn’t even them in the video. I didn’t see a name tag on the guy, but I don’t have the ability to enhance video etc.”

Ivan Orton, a King County prosecutor who has written books on cybercrime, also wrote Washington state’s statutes on computer trespass and malicious mischief. They are considered some of the stiffest cyberstalking laws in the United States.

The anonymity of the Internet makes people a lot ruder than they are in the real world, Orton said. While Washington created a cyberspace stalking law in 2004, the law is vague about what makes a cyberspace threat worthy of criminal investigation.

“The problem is that we are dealing with the ever-changing Internet and technology with laws that may have been outdated,” Orton said. “We will never win that battle.”

This incident also serves as a warning to people about the need to be careful about how they put personal information out on the Internet, said Mike Andrew, vice president of training and forensic analyst for the CyberSecurity Institute. The Monroe firm trains law enforcement and military agencies and corporations on cyberspace security.

“People don’t realize that there is a lot of information about themselves that they don’t know of,” Andrew said.

Reporter Yoshiaki Nohara: 425-339-3029 or ynohara@heraldnet.com.