Edmonton police have laid 460 charges against 34 teens following a wave of violent crimes at transit stations, malls and recreation centres.
In one case, police released video images of a teen kicking a woman down a flight of stairs who suffered severe internal injuries.
Investigators say in another case, some teens used social media to create a flash mob in a swarming attack on two teen boys.
The 34 accused range in age from 13 to 18 and the alleged crimes go back to January 2017.
The charges include aggravated assault, assault, robbery, weapons offences, theft under $5,000, possession of stolen property and other offences.
'Very serious' injuries: police
Supt. Tom Pallas says the suspects have left a path of victims across the city.
"Officers have responded to close to 90 criminal events involving 66 complainants, some of whom are now dealing with very serious internal and facial injuries," he said Wednesday in a release.
He said investigators believe 12 of the 34 suspects were involved in most of the crimes.
"Many of these individuals have been arrested, gone through the court system and rearrested by our officers, after being released on bail, in some cases within hours."
None of the accused can be named because they are either under 18 or were under 18 when the alleged crimes were committed.