WASHINGTON — The death toll in the latest US school shooting rose to four Wednesday after a 17-year-old student died from his wounds in the attack at a Michigan high school, local police said.

The Oakland County Sheriff’s office said in a statement that Justin Shilling, who was a student at Oxford High School in the rural town of Oxford, Michigan, succumbed to his wounds in the attack.

Police on Tuesday said that a 15-year-old male student opened fire with a semi-automatic handgun in the high school, shooting at least 30 rounds that have now left four students dead and six students and one teacher wounded.

There was no immediate explanation for the attack, which sent panic through the 1,800 students at the school, according to police.

The shooter used a nine millimeter Sig Sauer pistol that his father bought for him on November 26, the day after Thanksgiving known as “Black Friday” for massive sales put on by stores nationwide to launch the Christmas gift-shopping period, the police said.

The suspect, a second-year student, apparently brought the gun into school with a backpack and multiple ammunition magazines.

He surrendered to police in the hallway of the school, with several rounds still in the gun, they said.

Police said they had searched the home of the suspect. “This is expected to be a lengthy investigation and hundreds of interviews will be conducted,” they said in a statement.