Published: Aug 18, 2010 4:48 PM EDT
Updated: Aug 18, 2010 1:48 PM EDT

McKINNEY, Texas (AP) - A coroner says the gunman who pulled into a suburban Dallas police station parking lot with a trailer loaded with explosives and opened fire on officers committed suicide.

The Collin County Medical Examiner's Office said Wednesday that 29-year-old Patrick Gray Sharp died of a self-inflicted gunshot wound to the head.

Police say Sharp ended up in a shootout with authorities Tuesday morning after towing a trailer filled with explosives into the parking lot of the McKinney police station and setting his pickup truck on fire. Police say Sharp retreated to a field across a road and fired more than 100 rounds at police headquarters.

Sharp was found dead after exchanging gunfire with police.

The McKinney police chief says authorities don't have a motive.