CHICAGO – A medical helicopter pilot hit bad weather and was trying to return to the hospital shortly before the aircraft crashed into a northern Illinois field, killing him and two nurses, authorities said Tuesday.

Pilot Andy Olesen radioed to dispatchers at Rockford Memorial Hospital that he was turning around because he had “encountered some weather” while heading to another hospital to pick up a patient Monday night, hospital spokesman Wester Wuori said.

Olesen, 65, and flight nurses Karen Hollis, 48, and Jim Dillow, 40, died when the helicopter crashed about 8:30 p.m. near Rochelle, about 70 miles west of Chicago. No patients were aboard.