SLIDESHOW: Cars Hit, Windshields Smashed

The softball- and basketball-size rocks were thrown onto the southbound freeway about 2:15 a.m. near the 272nd Street exit, Trooper Cliff Pratt said. The largest rock weighed as much as 25 pounds.

Pratt said one rock went through the windshield of the driver's side of a semi-truck. He said the driver was treated at the scene by the Federal Way Fire Department, but did not have to go to a hospital.

Rocks also hit the sides of four other vehicles, including an SUV and a sedan.

Pratt said there was a witness report of a man walking on the side of I-5 about the time of the rock throwing. It's illegal to walk on the freeway, but he doesn't know if that was the person who threw the rocks.

Police said they believe the person who threw the rocks was an older teen or young adult.

Pratt asked anyone with any knowledge of the rock throwing to call the State Patrol at 425-649-4370.