Officers responded to the scene, in the 9800 block of State Avenue, at about 3 a.m. after receiving a 911 call from a relative, said Cmdr. Robb Lamoureux of the Marysville police.
The death was discovered by the victim's grandson when he went to check on him. The grandson told his mother, who called police.
Arriving at the scene, officers quickly determined the man's death was likely a homicide and called for detectives.
Lamoureux later said the victim's pickup truck is missing and he asked for the public's help in locating it. The pickup, a champagne-colored 2006 Chevrolet Colorado, has Washington license plate number B03681A.
It is presumed that it was stolen by the suspect or suspects involved in the homicide, Lamoureux said.
"We are considering the occupants as being armed and dangerous and ask that the public do not try to intervene. We simply want them to call 911 to report the location of the vehicle," he said.
No further details were immediately available. The name of the victim was not released pending notification of next of kin, but Lamoureux did confirm that the victim was a level III sex offender.