The teenager has been identified as Ryan Dube, who had been living at the Nightlight Youth Services residence in Niagara Falls, according to a statement Wednesday from the Boys and Girls Club of Niagara.
Niagara Regional Police Service identified the officer as Const. Jacob Smits.
Ontario's Special Investigations Unit says that shortly after 5 p.m. ET on Tuesday, an officer was chasing a man on foot on River Road, between Otter and Eastwood streets, roughly three kilometres downstream from the falls.
Shortly afterward, both went over a wall and into the deep, rocky gorge.
Rescue crews used a hard-framed basket attached to a fire truck boom to reach the victims, the CBC's Ivy Cuervo reported.
Police said the injured officer was airlifted to a hospital in Hamilton with a broken femur (thigh bone). The police have not provided an update on his condition, only saying in a news release that he underwent emergency surgery.
The Boys and Girls Club of Niagara said Dube had been staying at the Nightlight Youth Services residence.
"The youth had been at the residence off and on since 2011, without any issues of violence. Staff report that he was well-liked by staff and residents alike, good natured and always respectful," a statement said. "At 18, the youth had issues with making curfew on occasion, but was moving forward toward his personal goals."
'The kid went off the ledge'
Logan Tremblay was just steps away from the pair when he witnessed them tumbling over the gorge.
"The kid went off the ledge, and the cop went with him," he said, shaken.
"I ran over the ledge to see if I could grab the cop or if the cop was still on the ledge, and as I looked, the cop was going. Like I saw part of his uniform and then it disappeared."
The SIU, which investigates police incidents involving death, serious injury or sexual assault, has assigned seven investigators and two forensic investigators to the case.
Police have not revealed what led up to the chase, nor would they confirm reports from residents on River Road that gunshots were heard shortly before the pursuit.