ARLINGTON HEIGHTS, Ill. — An Illinois man arrested on charges that he opened fire on a motorist on Interstate 80 in eastern Iowa and exchanging gunfire with state troopers has told investigators he targeted truck drivers because he was angry over a fatal truck crash.

The (Arlington Heights) Daily Herald reports that a sheriff’s deputy in Cedar County, Iowa, explained in a search warrant application that Charles Johnston had become “obsessed’ with the crash and told investigators after his Jan. 11 arrest that he wanted to harm at least one trucker in retaliation.

The 60-year-Johnston is charged with attempted murder and assault on a peace officer with a dangerous weapon. He is being in Cedar County Jail on $1 million bail.

The paper reports that Johnston is a professor at Harper College in Palatine.