By Mai Martinez

(CBS) — The federal trial of a Chicago police officer who shot 16 times into a car full of teens –hitting two of them — got underway Tuesday.

CBS 2’s Mai Martinez was in court for opening statements.

Dash-cam video is a key piece of evidence in the federal case against officer Marco Proano.

Officer Proano responded to a call for help from fellow officers in pursuit of a possible stolen car in December 2013. As a car full of teens reversed, Proano opened fire on it — emptying his clip of 16 bullets. Two of the teens were hit.

In court, prosecutors called Proano’s actions unreasonable and excessive, but Proano’s attorney, Dan Herbert, said the officer did what he was trained to do. He questioned how the government could pursue a case against the officer after the feds have been critical of training by the Chicago Police Department.

Herbert went on to say the shooting took about three seconds, and Proano fired because he feared for his safety and the safety of one of the passengers who he thought was being dragged by the car.

Herbert also showed the jury a BB gun that looks like a real gun and said a similar firearm fell out of the car as one of the teens tried to flee.

Proano was suspended without pay after he was indicted last year. He and his attorney left the courthouse without talking to the media.

The trial is scheduled to resume Wednesday morning. Among the witnesses the government is expected to call is one of the teens shot by Proano.