PHOENIX - The pedestrian struck and killed by a semi on Loop 101 Wednesday night died by suicide, the Arizona Department of Transportation says.

The 17-year-old -- DPS initially said he was 24 -- was taken to a hospital in critical condition by Phoenix fire officials. He later died.

Northbound lanes were closed from Interstate 10 to Indian School Road into the night.

Northbound on-ramps from McDowell and Thomas roads were also closed.