(WBBM Newsradio) — Iowa investigators say a Harper College professor shot at state troopers and motorists along I-80, and they say they’re not sure why.

WBBM’s Jim Gudas reports.

It happened on Jan. 11.

Harper College Associate Psychology Professor Charles Johnston drove from his home in Belvidere along I-80 to Cedar County, Iowa, according to Special Agent Ryan Herman of the Iowa Department of Public Safety.

Herman says Johnston had an encounter with a truck driver, shot at people at a gas station and then exchanged fire with state troopers who finally arrested him.

No one was hurt.

“It was remarkable no one was injured – including Mr. Johnston,” Agent Herman says.

Johnston is charged with attempted murder and assault of a police officer with a dangerous weapon.

Herman says it’s unclear to investigators what the motive for the shooting spree might have been.