The Washington State Patrol is asking for the public's help to find the person who shot four cars along Highway 509 in Burien Wednesday.

The cars were traveling southbound on the highway between South 160th and South 188th streets. Troopers believe the gunman was on the east side of the freeway on a wooded embankment, based on the trajectory of the bullet holes.

That's near May Collins home which overlooks the freeway. She said her husband was home sick but heard the gunfire Wednesday afternoon.

"That's scary," Collins said. "I have kids."

The person left the area before police arrived.

"Someone that was maybe acting suspiciously or carrying a bag or a case of some kind," said Trooper Rick Johnson.

Johnson said investigators were canvassing the residential and business neighborhoods in that area looking for surveillance video that may have captured the gunman walking through the area. They said some cars have GoPro cameras mounted that could spot a pedestrian along the freeway.

WATCH: Gunman shoots cars along SR 509

WSP wouldn't say what the caliber was, but the rounds had power behind them.

"If a bullet enters a drivers door and exits through the passenger door completely, it's got some velocity," said Johnson. "I'm not a caliber guy, but there was some energy behind that round."

Anyone with information or video is asked to contact the Washington State Patrol.