• The critically injured mother held onto her child in the gruesome attack
  • The suspect had been in a relationship with the toddler's aunt
  • He attacked her with a knife but the woman fought back and killed him

Billings, Montana -- A man rammed his vehicle into a family walking by the road in Glacier County and opened fire at them, fatally shooting a 39-year-old father and his toddler, and critically injuring the mother, authorities said Tuesday.

The incident occurred shortly before 9 p.m. Sunday, in East Glacier Park when the attacker, identified as Derick Amos Madden drove straight into the family before crashing into a tree, Associated Press reported.

After firing his shotgun at the family, Madden attacked the toddler's aunt with a knife as he ran out of ammunition. But the woman, Christina Siau, 30, fought back and killed him, the Glacier County Sheriff's Office revealed.

The deceased father was identified as David Siau of Syracuse, New York, and the fatally injured child was his 18-month-old daughter, McKenzie. Christy Siau, the 40-year-old mother held onto her daughter as she was critically wounded in the gruesome attack.

McKenzie succumbed to her injuries at the Indian Health Service hospital in Browning, AP reported. Two other children who were present at the scene managed to escape and are safe, officials said.

The shooting occurred on the Blackfeet Indian Reservation, which neighbors Glacier National Park to the west and Canada to the north.

37-year-old Madden, who was from Goldsby, Oklahoma, suffered from "mental health issues," the sheriff's office revealed. He had been romantically involved with the toddler's aunt, Christina, NBC News reported.

“The investigation continues and detectives are working tirelessly to find all the details and circumstances surrounding this horrific event,” the sheriff’s office said.

Officials are yet to determine if the shotgun used by Madden was bought legally.

In a similar incident reported in May, a teen from England was sentenced to prison after he drove his car into his ex-partner and her friend in frenzied anger. Ryan Meggitt, 19, reportedly attacked his ex after she blocked him on Facebook. While the unidentified woman managed to jump out of the way, her friend was struck by Meggitt's speeding car. But her companion, who was also unidentified, was struck over and thrown over the car's bonnet in the chilling incident. Meggitt had confronted the two women before the incident and had reportedly slapped both of them.

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