High school student shot in leg while driving on I-15

UTAH COUNTY, Utah -- A high school student was shot in the leg while driving on I-15 in Utah County this week.
State investigator say this appears to be a random attack and are asking for help to find the person who fired the shot. 
Four young adults were traveling in the southbound lanes of I-15, driving from Salt Lake City to Orem just after noon Tuesday. Investigators said after they passed the Lehi Main Street exit they were shot at.
“Out of nowhere we hear this boom,” said Ana who was in the car.
A single bullet shot right through the back passenger side door.
“It was very loud, as if something really hard fell to the ground,” Ana said.
The four young adults in the car assumed the speaker in the door exploded. Then the 18-year-old in the backseat started yelling in pain. 
“He just started grabbing onto me and i started freaking out because i saw blood on the floor,” Ana said.
She assumed a piece of plastic from the cars speaker went through his leg. 
“I was like - pull over he's bleeding,” Ana said.
Then the driver, who is the teen's cousin, rushed over to him.
“I pulled his pants up and you could see the hole on one side," said Vennessa, who was driving the car.
They had no idea that bump was a 9 millimeter bullet until they got to the hospital. 
“Then I saw the hole in my car door and then I was like 'oh my God, you got shot,” Vennessa said. 
The bullet was lodged in the teens calf, right below his knee. His loved ones say a difference of a few inches could have killed him. 
“I’m thankful it's just his leg his lower leg and he'll be able to recover, if God's willing, and he'll be able to walk again,” Vennessa said.
Investigators say this appears to be a random shooting.
If you have any information on the shooting call Utah Highway Patrol at 801-887-3800.