A man who drove his truck into a family of five vacationing in Montana, then opened fire on them with a shotgun, had raised “red flags” regarding his mental health in the years prior, according to his sister, and was only stopped when the apparent target of his rage managed to fight back and kill him with his own knife.
After hopping out of his truck, Derick Amos Madden, 37, fatally gunned down 39-year-old David Siau and his 18-month-old daughter McKenzie, who were visiting from Pompey, New York, authorities said. Siau’s wife, Christy, was critically wounded but survived the roadside ambush Sunday. The couple’s two other children were able to flee to safety, miraculously escaping injury.
Madden’s apparent target had been his ex-girlfriend, 30-year-old Christina Siau. Christina, David’s sister, lived in East Glacier and worked as a physician assistant at a hospital serving the Native American community. When Madden ran out of ammunition, he drew a knife and began stabbing Christina, according to cops. At some point during the gruesome rampage, Christina, badly wounded, managed to kill Madden at the scene.
Although police have not yet revealed how Madden died, his sister said on Wednesday that investigators informed her that Christine at one point managed to wrest the knife away from Madden, stabbing him to death.
“We have no idea why [he did it],” Michelle Madden, 38, told The Daily Beast, expressing her condolences to the Siau family.
Michelle, who still lives in Oklahoma, where she and Madden grew up, said she is in a state of shock. Madden had been on-and-off with Christine for the last 10 years, and he battled ongoing depression along with a range of other psychological issues, she said.
“My brother… suffered from mental illness and had a brain injury, where they had to put it all back together,” she said. “He wasn’t supposed to drink on his medication, the medication he took every single day. But he had been. In the past, he had multiple instances where he would go sleepwalking and not remember any of it. It only happened when he was drinking on his medicine. That’s the only thing I can think of.”
Speaking to The Daily Beast by phone on Wednesday, Michaela Siau Pfohl, David and Christina Siau’s sister, asked the public for privacy as the family grieves. A fundraiser has been set up to help the surviving members of the Siau family with expenses.
“You can definitely share the GoFundMe, because while money isn’t going to fix all the problems, it will help my sister and sister-in-law as we try to step forward from this,” Pfohl said.
Michael Mazzye, the pastor of Renovation Church in North Syracuse, described David and Christy Siau as “caring, sweet people who are thoughtful of others.”
“I can’t imagine this horrible tragedy,” Mazzye told Syracuse.com. “It’s unthinkable.”
Christina has worked at the Indian Health Service’s hospital in Browning—the same hospital that treated the 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 with those who were injured as they fight to recover from this horrific event,” the spokesperson said.
Madden spent roughly a decade serving in the Oklahoma National Guard, and was assigned to the 63rd Civil Support Team, a National Guard spokesman told The Daily Beast. The unit is tasked with providing “expert support to civilian first responders in the event of a chemical, biological, nuclear, radiological and high yield explosive-related emergencies.”
Madden left the Guard on April 3, 2013, and “we’ve had no other interactions with him since he separated,” the spokesman said.
During his hitch, Madden deployed to Afghanistan, according to Michelle. Madden returned home plagued by his experience, and his mental health complications “stemmed from that,” according to his sister.
“He had been diagnosed with borderline personality disorder, bipolar disorder, and PTSD,” Michelle said. “Combined with him drinking on his meds, he just could not process life.”
A soldier who served alongside Madden said he had been awarded a Bronze Star for valor while overseas.
“His unit from that mission has been reeling over the past 24 hours trying to figure out what any of us could have done differently,” Alexander Christine told The Daily Beast. “... I hate myself for not staying connected with him.”
Michelle described her brother as “very closed in,” 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 problems 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 to Facebook, cradling a rifle in his lap and making a devilish face, with the caption, “i like to clean my gun!”
“There [were] red flags, I’m sure, for the people who were around him,” Michelle said. “But to me and his nephews, he was really good at just putting on a poker face, I guess.”
Madden seemed to have an emotional setback shortly before the unthinkable attack, according to Michelle. Her 15-year-old son had flown out to Montana to visit with Madden for three weeks, who then drove his nephew back to Oklahoma. He spent the night at his Michelle’s place, with a plan to hit the road back to Montana the next day.
While he was there, Madden told his sister that Christina had contacted him out of the blue, taking him by surprise.
“The last thing I spoke to him about in person was that Christina had checked on him to see how his winter was,” Michelle said. “He had been really close to getting over her, and he was confused by it… I didn’t think that he was really that much into her anymore… But I think he had a problem letting her go for some reason, even though he wasn’t really romantically wanting her… I don’t know if it was an ego thing, or just not wanting to be alone.”
Michelle said she watched Madden’s personality undergo a seismic shift following his stint in the military.
“He never would have done anything like this [if he was] in his right mind,” she insisted. “That doesn’t make any of it OK… It doesn’t matter if he meant to do it or not. You can’t undo any of it, you can’t bring any of those people back.”
It is especially painful to Michelle that Madden’s youngest victim, McKenzie, shares a name with her own daughter—Madden’s niece.
“Her name is spelled the same way as the child he murdered,” Michelle said through tears. “I mean, who can do that?”
In the meantime, she is left struggling to make some sense of a senseless crime.
“He just snapped, is all I can think of,” she said. “He did a horrible, horrible thing… And now I have to remember him forever for killing this family. And for what?”
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