His office said Wednesday that he remains in Dallas with his family and has canceled his immediate schedule of meetings and public events, including a planned trip this week to Sapporo, Japan, for the APEC meeting of Ministers Related to Trade.
Deputy U.S. Trade Representative Demetrios Marantis will lead the office's delegation to the APEC meeting.
A tractor-trailer traveling ahead of Kirk's Mercedes struck the ladder that had been fallen onto the interstate, causing it to fly into Kirk's car, police said. Kirk's passenger was not injured.
Police don't know how the ladder got onto the interstate and said no markings identify the owner. They said it apparently fell out of another vehicle a few minutes earlier.
