Peter Hendy II beat his girlfriend’s 4-year-old son so badly that he severed his liver in three places and left fist marks on his stomach, prosecutors said. Then, as the boy lay dying, Hendy left him alone and went out to sell marijuana on the streets.

On Friday, a D.C. Superior Court judge sentenced Hendy to 20 years in prison after he pleaded guilty to one count of second-degree murder in the August beating death of Kamari Zavon Taylor.

Hendy, 33, was dating Taylor’s mother, who left her son with him in a Northeast Washington apartment when she went to work, authorities said. Hendy scolded Kamari for riding a scooter, and when the child told him, “I don’t have to listen to you — you’re not my daddy,” Hendy flew into a rage and punched him four or five times, prosecutors said.

At the emotional sentencing hearing, Hendy stood next to his attorney and faced Kamari’s mother and nearly 30 other relatives who had assembled in the courtroom. “There are no amount of sorrys. No words for the sorry I have,” Hendy said, his wrists and ankles shackled. “This was unintentional. I’m sorry. ”

Judge Ronna L. Beck followed the sentencing agreement outlined in a September plea arrangement with prosecutors. Beck praised Hendy for taking responsibility so quickly, and acknowledged that he had a history of mental illness and anger problems, which Hendy’s attorney said contributed to the Aug. 5 slaying.

Hendy’s relatives sat on one side of the courtroom, and Kamari’s family sat on the other. Hendy’s relatives wiped away tears as Kamari’s great-aunt Armanda Brown told the judge how the boy’s death affected the family.

“My family has never experienced loss like this. My niece is so distraught, we have her on suicide watch,” Brown said, referring to Kamari’s mother, Calesenia Ferguson.

Ferguson, 22, sat nearby, sobbing and rocking back and forth as relatives and a counselor with the U.S. attorney’s office comforted her.

Prosecutors said Hendy had a history of violence toward women, including Ferguson.The judge placed Hendy on five years of supervised release after his release from prison. Hendy also faces deportation to his native Guyana after he is released.

Outside the courthouse, Kamari’s father, Kelfa Taylor, 23, smoked a cigarette and said he had hoped that Hendy would be sentenced to life in prison. “He was my heart,” Taylor said of Kamari.

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