London police have upgraded the charges against accused killer Robert Ashley Williams to first-degree murder in connection with the May death of fitness trainer Dereck Szaflarski.

Szaflarski was killed in the area of Richmond and Piccadilly Streets, following an altercation only a few hours after a night on the town celebrating his 27th birthday in late May.

Since then, investigators have neither said whether a weapon was involved in the dispute, nor have they released Szaflarski's cause of death.

On Thursday, homicide investigators announced they believed Williams had thought out a plan to kill Szaflarski, upgrading the charges against Williams from second-degree to first-degree murder.

Popular fitness trainer

Robert Ashley Williams is wanted by police in connection with the death of a 27-year-old London man on May 26, 2018

Szaflarski was a popular fitness trainer, known as a social butterfly with a sense of humour, who was also an ambitious entrepreneur with plans to grow his burgeoning deck and fence company.

Williams, 35, was arrested when he turned himself into authorities six days after Szaflarski's death.

During a court appearance, he stood in the prisoner's box with a heavily bandaged arm, which his lawyer Jim Dean called "a significant injury."

Dean said Williams underwent surgery for the injury and noted his client faces a number of other medical problems, including what the lawyer referred to as some "very serious illnesses," some of which he said are life-threatening, noting he couldn't go into specific detail at the time.

Williams was scheduled to appear in court Thursday to answer to the new charges in his case.