Liam Deane, a British man sentenced to life in prison for the murder of his newborn daughter, was found dead just one month into his sentence. Authorities say he was allegedly killed by fellow inmate John Westland, who has since appeared in court in connection with Deane’s death.

Deane had confessed to violently shaking and punching his 2-day-old daughter, Luna, because she wouldn’t stop crying. Luna died three days later from severe brain injuries. He was convicted and sentenced to life for her murder.

“He admitted causing all of Luna’s injuries,” the prosecutor said during Deane’s trial, according to The Mirror. “He said she wouldn’t settle and he lost control.”

“There is simply no explanation for the defendant’s actions,” said Richard Wright, the attorney who represented Deane in court in Leeds, England.