A man was attending a memorial service for a homicide victim when he was shot dead in a waterfront park in downtown Toronto, investigators said Monday as they called on witnesses to come forward.

Det. Amanda Thornton told reporters that 30-year-old Michael Lewis of Markham, Ont., was with his two children and his pregnant wife when he was shot multiple times at close range on Sunday evening at Coronation Park.

"Shortly before the 911 call, four males approached Mr. Lewis, who was in the park attending a memorial for a male who had been a homicide victim nine years ago," said Thornton.

Police tape marks the scene Monday where gunshots rang out Sunday evening. (Martin Trainor/CBC)

Four deadly shootings in GTA within 24 hours

She said the four men had a brief discussion with Lewis before one of the men allegedly pulled out a handgun and shot Lewis multiple times.

"Mr. Lewis collapsed to the ground and the suspects fled the park," Thornton said.

He died at the scene, she said, adding that it had been a busy day at the park where families were trying to enjoy the long weekend.

"His partner was present at the time as were two of his children," Thornton told reporters on Monday.

His death marked the fourth fatal shooting in the Greater Toronto Area in 24 hours.

Investigators believe the suspects and Lewis knew each other, Thornton said, adding that 30 or 40 people were in the park at the time of the shooting.

"Because of the obvious chaos they fled in all directions," she said. "I'm requesting that if you were in the park at the time of the homicide or were in attendance of the memorial, to please contact the homicide squad."