Police said a Tonawanda resident jumped to his death from the center of the Rainbow Bridge about 6:30 p.m. Friday.
The victim was identified as Peter Snyder, 19, of 162 Wendover Ave.
Detective John Donner said the youth's father, Peter Snyder Sr., said they were walking to the United States from Canada with the son walking a short distance ahead.
"The father said he looked away momentarily and the boy jumped over the railing, falling several hundred feet," Donner said.
The body was recovered near the Maid of the Mist landing and taken to a funeral home in Niagara Falls, Ont. Dr. John O'Neill, the coroner, is investigating.
Donner said the victim had been under psychiatric care, according to his father.