Two survivors of a West Virginia mine blast have since committed suicide, the Associated Press reported. The two miners, John Nelson Boni, a fireboss, and William Lee Chisolm, a dispatcher, were questioned by investigators in the aftermath of the Jan. 2 explosion at Sago Mine, which led to the deaths of 12 of their coworkers.

Neither was blamed in the tragedy, and police said it’s not clear why they committed suicide. But J. Davitt McAteer, West Virginia Gov. Joe Manchin’s adviser on the accident, said such incidents weigh heavily on those involved.

“Traumatic events have a long-lasting effect on people,” said McAteer. “We have to be careful and conscious of this fact and provide as much counseling and support as we can.”

State police were called to John Boni’s home in Volga early Saturday. They found him dead of a gunshot to the head, said Sgt. James Merrill. He’d been talking to his father-in-law on the phone when the father-in-law heard a shot. His ex-wife, Vickie Boni, said she doesn’t know why he killed himself but the tragedy continued to bother him. “I’m not sure anybody ever gets over it,” said Boni. “You live with it every day.”

On Aug. 29, Randolph County sheriff’s officers found Chisolm, who had been monitoring carbon monoxide levels the day of the blast, dead from a gunshot wound in his Harding-area home. Chisolm had told investigators that a carbon monoxide alarm sounded about 20 minutes before the explosion, but he thought it was malfunctioning. Investigators were satisfied that the alarm probably wasn’t related to the cause of the explosion.