Investigators now believe Mark McCreadie was strangled to death – and the man accused of attacking him now faces a charge of first-degree murder.

The body of McCreadie, 50, was found in April, in a wooded area near Victoria Park.

Days later, 52-year-old Derrick Lawlor was charged with aggravated assault.

At the time, Waterloo Regional Police said the incident that led to the assault charge was not the same altercation that led to McCreadie's death.

Tuesday, police said continued investigation led them to the conclusion that McCreadie was strangled, and allege Lawlor was behind that act, prompting the upgrading of charges against the Waterloo man.

Additionally, police now say they want to hear from anyone who “may have engaged in intimate physical or sexual activity” with Lawlor in the last few months.

Lawlor – who had an employment contract with the University of Waterloo until May 1, although sources tell CTV News he was on long-term leave from the school at the time of McCreadie's death – made a brief court appearance Tuesday, during which family members of McCreadie were present.

Tammy McCreadie, his daughter, declined an on-camera interview, but called her father an outgoing and kind-hearted man who moved to the area in 2012 to take care of his mother.

Police say they don’t anticipate any further arrests.

Anyone with information is asked to contact police at 519-653-7700 ext. 8666 or Crime Stoppers at 1-800-222-8477.