After getting out of his truck, Derick Amos Madden, 37, fatally shot 39-year-old David Siau and his 18-month-old daughter McKenzie, who were visiting from Pompey, New York, authorities said. Xiao’s wife, Christy, was seriously injured but survived Sunday’s roadside ambush. The couple’s other two children managed to escape to safety, miraculously escaping injury. Madden’s apparent target was his ex-girlfriend, 30-year-old Christina Siau. Christina, David’s sister, lived in East Glacier and worked as a physician’s assistant at a hospital that served the Native American community. When Madden ran out of ammunition, he pulled out a knife and began stabbing Christina, according to police. At some point during the gruesome rampage, Christina, badly injured, managed to kill Madden on the spot. Although police have not yet released how Madden died, his sister said Wednesday that investigators told her that Christine at one point managed to wrestle the knife away from Madden, stabbing him to death. “We have no idea why [he did it]Michelle Madden, 38, told The Daily Beast, offering her condolences to the Siau family. Michelle, who still lives in Oklahoma, where she and Madden grew up, said she is in shock. Madden has been with Christine for the past 10 years and has struggled with ongoing depression along with a host of other psychological issues, he said. “My brother … suffered from mental illness and had a brain injury where they had to put it all together,” she said. “He shouldn’t have been drinking with his medication, the medication he was taking every day. But it was. In the past, he had many occasions where he sleepwalked and remembered nothing of it. It only happened when he drank with his medicine. That’s the only thing I can think of.” The Siau family, left and Christina Siau, right.
Photo illustration Luis G. Rendon/The Daily Beast/Bethany Siau/GoFundMe
Speaking to The Daily Beast by phone Wednesday, Michaela Siau Pfohl, the sister of David and Christina Siau, asked the public for privacy as the family grieves. A fundraiser has been set up to help the surviving members of the Xiao family with expenses. “You can definitely share the GoFundMe, because while the money isn’t going to fix all the problems, it will help my sister and sister-in-law as we try to move forward with this,” Pfohl said. Michael Mazie, the pastor of the Reformation Church in North Syracuse, described David and Christy Xiao as “caring, sweet people who look out for others.” “I can’t imagine this horrible tragedy,” Mazzye told Syracuse.com. “It’s unthinkable.” Christina has been working at the Indian Health Service hospital in Browning — the same hospital that treated Siaus on Sunday — since 2019, a spokesperson told The Daily Beast in an email. “Our hearts go out to the families of the victims at this difficult time and to those injured as they struggle to recover from this horrific event,” the spokesman said. Madden spent about a decade serving in the Oklahoma National Guard and was assigned to the 63rd Civil Support Group, a National Guard spokesman told the Daily Beast. The unit is tasked with providing “specialized support to civilian first responders in an emergency involving chemical, biological, nuclear, radiological and high-yield explosives.” Madden left the Guard on April 3, 2013, and “we have had no further interactions with him since his separation,” the spokesman said. Derick Madden, right, in 2011 helps after a tornado hit while serving in the Oklahoma National Guard.
Photo illustration by Luis G. Rendon/The Daily Beast/Alamy
During his fight, Madden was deployed to Afghanistan, according to Michelle. Madden returned home plagued by the experience, and his mental health complications “stemmed from that,” according to his sister. “She had been diagnosed with borderline personality disorder, bipolar disorder and PTSD,” Michelle said. “Combined with him drinking with his medication, he just couldn’t process life.” Michelle described her brother as “very closed off”, with so few close relationships in his life that she could count them “on one hand”. Madden had been committed to a VA hospital for psychiatric issues at least once before, and the system “should have been more aware of his mental state,” Michelle argued. In 2005, Madden posted a photo of himself on Facebook, holding a rifle in his lap and making a devilish face, with the caption “I love to clean my gun!”. Derick Madden cleaning a gun in an old Facebook post.
Photo illustration Luis G. Rendon/The Daily Beast/Facebook
“There [were] red flags, I’m sure, for the people who were around him,” Michelle said. “But for me and his nephews, he was pretty good at just putting on a poker face, I guess.” Madden appeared to be having an emotional setback shortly before the unthinkable attack, according to Michelle. Her 15-year-old son had flown to Montana to visit Madden for three weeks, who then drove his nephew back to Oklahoma. He spent the night at his Michelle’s house, planning to hit the road back to Montana the next day. While there, Madden told his sister that Christina contacted him out of the blue, taking him by surprise. “The last thing I talked to him about personally was that Christina had checked on him to see how his winter was,” Michelle said. “He was so close to getting over her, and he was confused about it… I didn’t think he loved her that much anymore… But I think he had trouble letting her go for some reason, even though I didn’t really want her romantically… I don’t know if it was a matter of selfishness or I just didn’t want to be alone.” Michelle said she watched Madden’s personality undergo a seismic shift after his time in the military. “He would never do such a thing [if he was] in his right mind,” she insisted. “That doesn’t make any of it okay… It doesn’t matter if he wanted to do it or not. You can’t undo any of that, you can’t bring any of these people back.” It’s especially painful for Michelle that Madden’s newest victim, MacKenzie, shares a name with her daughter—Madden’s niece. “Her name is spelled the same way as the kid she murdered,” Michelle said through tears. “I mean, who can do that?” Meanwhile, he is left struggling to make sense of a senseless crime. “It just broke, that’s all I can think about,” he said. “He did a horrible, horrible thing… And now I have to remember him forever for killing this family. And why;”
