Joseph Lester, 25, was convicted last month of second degree murder in the stabbing death of 21-year-old Keisha Lewis.
"This is a sad and disturbing example of domestic violence," Prosecutor Mark Lindquist said in a statement. "The defendant's murderous rage leaves Keisha Lewis' two young children without their mother. While we believe a longer sentence would have been more just, the defendant has been held accountable."
On Halloween night in 2011, Lester showed up at the victim's University Place home with the couple's 9-month-old daughter. Prosecutors say he and Lewis began to argue outside the apartment, and moments later witnesses heard Lewis cry out, "He's killing me," according to court papers.
Lewis was able to make it back inside, where her mom, best friend and 2-year-old son were located, but she was bleeding heavily from multiple stab wounds and died before she could be taken to a hospital. She was at least two months pregnant when she was killed.
Lester grabbed his young daughter and sped away from the apartment. A witness told authorities that Lester said, "I'm doing to her what she did to me."
Lester turned himself in several hours later.
During his murder trial, Lester claimed he was suffering from post traumatic stress disorder at the time of the attack and was defending himself from Lewis. But an autopsy showed Lewis had been stabbed multiple times, including fatal wounds to the head and the throat, according to prosecutors.
Prosecutors asked for an exceptional sentence of 50 years because Lester knew Lewis was pregnant and the crime occurred in the presence of their child.
Tensions between the Lester and Lewis families boiled over after the sentence was announced and one of Lester's supporters taunted a Lewis family member, saying, "He's going to get out."
That sparked several fist fights in the courtroom that only ended when a police officer used a Taser on one of the combatants.
The sentence was not nearly long enough for the victim's mother.
"Joseph's going to go to prison and he's going to come out worse when he gets out, and people are going to have to be afraid, including my family, and we're caring for his children," she said.