CONWAY, Wash. – Ethan Chapin’s last day was spent with his siblings, dressed up and dancing.

The Mount Vernon High School graduate was one of four University of Idaho students stabbed to death last weekend.

Ethan was a triplet, and his brother and sister also attend the scenic school tucked away in the rolling hills of north-central Idaho.

Their mother, Stacy Chapin, spoke with NBC News.

“We have these other two kids that are very impacted by this,” said Chapin. “And they need to be lifted up and cared for.”

The three 20-year-old siblings attended a dance hosted by Ethan’s sister Maizie’s sorority earlier on the night Ethan was killed.

He was dating 20-year-old Xana Kernodle, a junior who was also killed in the attack inside her rental home near the university campus.

Two of Kernodle’s roommates and friends, 21-year-old Madison Mogen and 21-year-old Kaylee Goncalves, were also killed in the attack.

Police have yet to find a suspect or a murder weapon.