Michael Chadd Boysen, the Renton man convicted in the 2013 killing of his grandparents, died Wednesday at the Washington State Penitentiary in Walla Walla.

According to a press release, Boysen, 28, returned to his cell at approximately 7:40 a.m. after taking a shower and lost consciousness. Staff attempted life–saving measures, but Boysen was pronounced dead at approximately 8:10 a.m.

Boysen had served 16 months of a life sentence without the possibility of parole for the March 2013 murders of Robert and Norma Taylor, just hours after they picked him up from a state prison in Monroe.

Following the murders, Boysen fled to Lincoln City, Ore., where he was arrested after an hours-long standoff with police.

After his arrest, Boysen railed against the poor treatment he received by the legal system and in the King County Jail, when he was held for about seven months.

He also attempted suicide in jail and was treated at Harborview Medical Center 16 times.

A cause of death has not yet been released, but the Department of Corrections is investigating the death.