PORTLAND — The city’s school community is in mourning today after a Portland High School student athlete was killed in a motor vehicle accident in Falmouth on Thursday night.

Garrett Cormier, 16, was heading home from his girlfriend’s house in Windham at 11:10 p.m. when he lost control of the sport utility vehicle he was driving on Blackstrap Road, said Falmouth Police Sgt. George Savidge.

“He had called his mother and told her he was on his way home,” said Portland High Principal Mike Johnson. Cormier had just completed his sophomore year.

Near 134 Blackstrap Road, the SUV left the pavement, hit a tree and rolled over, Savidge said. Cormier was wearing a seatbelt, he said.

Police said speed and driver inexperience contributed to the crash. Cormier got his license about six months ago.

Cormier was pronounced dead at the scene. Cormier’s mother, who was out looking for him because he hadn’t arrived home, came upon the scene shortly after police, Savidge said.

Cormier was well known in Portland schools because, in part, he was a son of Lauren Cormier, a social studies teacher at Lyman Moore Middle School, and Joseph Cormier, a former custodian at Portland High.

“This is every parent’s nightmare and every school’s nightmare,” said Johnson, who met briefly today with the family to express condolences and offer whatever support they need.

Johnson said counselors were available at the high school today if staff members or students needed support. On Saturday, the high school will be open from 9 to 11 a.m. and Lyman Moore Middle School will be open from noon to 3 p.m. for any students who need to talk.

Johnson and other school staff members described Cormier as a gregarious and considerate boy who was a good student and athlete. He had been a member of the football, wrestling and lacrosse teams and had planned to go to college, Johnson said.

“I’ve known him since he was a baby,” said Liz Bryant, one of several school secretaries who said they were fond of Cormier. “He was the type of kid who would call his friends and say, ‘I’m taking my sister out to dinner and a movie. Wanna come with us?’ “

Cormier leaves behind an older brother, Patrick, who will be a senior at Portland High in the fall, and a younger sister, Taylor.

The Portland High lacrosse team, of which Patrick Cormier is a member, is expected to call for a moment of silence and wear black leg bands when it faces Scarborough High School in the Class A state championship game on Saturday evening, said Athletic Director Rich Drummond.

Staff Writers David Hench and Jenn Menendez contributed to this story.