Josef Slezak, 37, pleaded guilty to four counts of vehicular homicide and one count of vehicular homicide of an unborn fetus and as part of a plea agreement, he was sentenced to 20 years in prison, the Nebraska Radio Network reported Wednesday.
Prosecutors said Slezak ran into the back of a vehicle that was stopped in traffic on Interstate 80 in western Nebraska in September, 2012. Killed in the crash were Christopher Schmidt, Diana Schmidt and their two children; 3-year-old Samuel Schmidt and 2-year-old Conner Schmidt. Diana Schmidt was about 30 weeks pregnant at the time.
The Schmidts were in the process of moving to California from Maryland.
An investigation found that Slezak had fallen asleep at the wheel shortly before the crash.
Notable deaths of 2014 [PHOTOS]