A man struck a family with his vehicle as they were walking beside a roadway near Glacier National Park in Montana on Sunday and then fired at them with a shotgun, killing a man and his 18-month-old daughter, the authorities said.
The gunman also critically injured two other members of the family; one of them fatally wounded him after he attacked her with a knife, the Glacier County Sheriff’s Office said in a statement.
The victims who were fatally shot were identified as David Siau, 39, and his daughter McKenzie, of Syracuse, N.Y. The authorities said Mr. Siau and his family had been visiting the town of East Glacier Park, in Montana’s Rocky Mountains, when the attack occurred.
Two other members of the family, Christy Siau, 40, and Christina Siau, 30, of East Glacier Park, were critically injured in the attack, the authorities said. A GoFundMe page identified Christy Siau as Mr. Siau’s wife and Christina Siau as his sister.
The Glacier County Sheriff’s Office identified the gunman as Derick Amos Madden, 37, of Goldsby, Okla. The sheriff’s office did not give a motive for the attack, but said that Mr. Madden had previously been in a relationship with Christina Siau, and that he had unspecified “mental health issues.”
Just before 9 p.m. local time on Sunday, Mr. Madden “purposely drove his vehicle” into the family and, after crashing it into a tree, got out, armed with a shotgun, and “began shooting at the same victims he had just hit or attempted to hit with his vehicle,” the sheriff’s office said in a statement.
Mr. Madden fatally shot Mr. Siau and then continued shooting at the rest of the family as they were running away, according to the sheriff’s office. He injured Mr. Siau’s wife, Christy Siau, and killed their 18-month-old daughter, McKenzie, who was being held by her mother, the authorities said.
Mr. Madden attacked Christina Siau with a knife, the sheriff’s office said. “During this attack Christina fought for her life and, despite receiving critical injuries,” the authorities added, “fatally wounded Madden,” who died at the scene.
Two other children were present, but were able to run away and were not injured, the sheriff’s office said.
The authorities said the two women and the 18-month-old were taken to a hospital in Browning, Mont., which is about 13 miles northeast of East Glacier Park. The child was pronounced dead at the hospital, and the two women were flown elsewhere to receive more intensive care for “critical injuries,” they said.
The attack was “isolated to this incident,” the sheriff’s office added, “with a clear nexus between the victims and Madden.” The investigation is ongoing, the sheriff’s office said.
On Wednesday night, the Federal Bureau of Investigation released a video statement from John Siau, the father of David and grandfather of McKenzie. He recounted what he said he had told his other children.
“Grieve, be sad, but don’t harbor anger about what has happened,” he said, “because what we have seen is actually the result of somebody who has harbored anger in his own life and allowed it to fester and allowed it to grow and develop into something very terrible and unspeakable.” He went on to quote passages from the Lord’s Prayer and said, “Our goal is to forgive.”
Mr. Madden was formerly a member of the Oklahoma National Guard, but left around 2013 and had no further contact with the organization, said Lt. Col. Geoff Legler, a spokesman for the guard.
Colonel Legler said that Mr. Madden was a chemical operations specialist and had been trained in how to identify dangerous chemicals and render some of them inert. Colonel Legler said he did not know Mr. Madden personally.
Public records indicate that Mr. Madden had lived in Oklahoma for several years.
A friend of Christina Siau, Haley Driver, described her as “calm, cool and collected and such a joy to be around.” Ms. Driver said that Ms. Siau, who is a physician assistant, was planning to move back to upstate New York after almost four years in Montana, having recently accepted a job in Ithaca, N.Y.
“She’s such a tough person,” Ms. Driver said in a Facebook message. “I admire her so much for who she is and the value she brings to our lives.”
The Siau family were active members of the baptist church community in upstate New York.
“We are mourning with the Siau and Brownell Families and will come alongside them during this time of unimaginable grief,” Justin Baratta, who works at the Missio Church in Syracuse, N.Y., said in an email. “It is certainly a broken world.”
Bethany Siau, the sister of David and Christina, set up a GoFundMe page to help with the family’s medical expenses.
“The number of people already reaching out and offering to help is incredible,” she wrote on the fund-raising site. “We appreciate you all.”
Alex Traub contributed reporting.