Three Colorado teenagers have been formally charged with murder after being arrested in connection with a rock-throwing spree that killed a driver. Joseph Koenig, Nicholas “Mitch” Karol-Chik, and Zachary Kwak, all 18-year-old high school seniors, face a dozen other counts for allegedly throwing large landscaping rocks towards seven vehicles on suburban Denver roads on April 19. The final rock-throwing incident killed 20-year-old driver Alexa Bartell, while three other people were injured.The Colorado First Judicial District Attorney’s Office announced on Wednesday that the three teenagers have now formally been charged with one count of murder in the first degree, with extreme indifference, as well as six counts of criminal attempt to commit murder in the first degree, three counts of assault in the second degree, and three counts of criminal attempt to commit assault in the second degree. “Based on the available facts and after careful legal analysis, we have filed charges and will now move forward with a criminal prosecution,” said First Judicial District Attorney Alexis King in a statement. “It is important to remember that these individuals are presumed innocent unless and until they are proven guilty. As in every case, our goal is to seek justice.”The defendants are being held without bond and appeared in court on Wednesday for the return filing of charges. The families of the accused declined to talk to the media or identify themselves. Karol-Chik and Koenig had allegedly thrown rocks at cars on at least ten separate occasions since February, according to court documents. Karol-Chik allegedly told police that on April 19, all three teens threw rocks at cars, and they were “excited” when they hit them. He allegedly said Kwak was the one who threw the fatal rock at Bartell’s car.After Bartell’s car was hit, Kwak allegedly said, “We have to go back to see that,” and when they turned around, Kwak allegedly took a photo of Bartell’s car “as a memento,” according to the documents. The next hearing in the case has been scheduled for May 16. The tragedy has shocked the community and highlighted the importance of safe driving and responsible behavior on the roads.