Wootton High School in Rockville, pictured on Aug. 31. (Bill O'Leary/The Washington Post)

They had just left one underage drinking party and were headed to another, four teenagers in an Acura flying down a dark road on a summer night.

The 18-year-old driver, Sam Ellis, a recent graduate and the star quarterback of Montgomery County’s Wootton High School, worried aloud about a speed camera ahead. Someone else in the car had an answer: If they went fast enough, the camera couldn’t catch them.

“We felt invincible,” a passenger would later tell police, noting that at one point he saw the speedometer top 100 mph. The driver’s eyes got wide and his jaw dropped. A teenager in the back seat let out a faint scream.

The car, driving for a time on the wrong side of the road, veered back across a double-yellow line as it entered a curve. Out of control, the car went off the road, went airborne, hit a fence and two trees, and flipped. Two teenagers, unbelted in the back seat, were instantly killed. Beer cans, still cold and sweating, were strewn nearby.

That account of the fatal crash on the night of June 25 — and the first details of the party that preceded it — are laid out in a new 26-page police accident report The Washington Post obtained Friday. The report tells a story not just of the wreck but of the broader culture of underage drinking that so often leads to tragedy in Montgomery County and in communities across the country.

According to the report, the four teenagers had just been at a party with about 25 other people at a friend’s house in North Potomac, Md. Guests brought vodka and beer. Witnesses told police that the father of the girl hosting the party was home and, though he did not provide the alcohol or serve it, he allegedly joked with a boy carrying two 30-packs of beer into the house, asking whether “one of the 30 packs was for him,” according to the report.

“I would not say it was casual drinking, I mean it was a party,” a 16-year-old witness told police.

Partygoers told police that it was not an overly raucous event but rather a gathering of friends to wish one of them well before she headed to Costa Rica for a community service trip. A 21-year-old bought vodka for the girls, and a 17-year-old used a fake Ohio driver’s license to buy the beer at a local store. The teens played beer pong and did shots.

“People were casually drinking, hanging out, relaxing,” said the car passenger who survived, according to the report. He said he thought the father believed fewer people were in the house. “Ten people or so played beer pong. I’m sure some people were drunk, but no one was puking or outrageous. At about 11:35-11:40, they ran out of beer.”

And when the party was winding down, a popular, college-bound athlete offered some friends a ride. They played loud music and “whipped” — a term one teen used to describe excessive speeding. And then crashed.

“This is another needless tragedy that has occurred as a result of an underage drinking party,” Montgomery County Police Capt. Tom Didone said. “Over the past few years, community acceptance of underage drinking has rivaled back into the early ’90s, in which parents continue to host parties, teens believe they’re entitled to a rite of passage to drink and that fatal collisions involving teens and alcohol are becoming an annual event. It is really important that people realize that underage drinking kills.”

No charges have been filed in the case, but police said Friday that prosecutors would be making decisions within the next month.

Ellis’s attorney, Michael Mc­Auliffe, declined to comment on specific findings in the report. But he said his client feels devastated.

“He understands the seriousness of the situation,” McAuliffe said. “He is in mourning for his dead friends. His whole family is in mourning. It’s an awful situation for everyone involved.”

The father who allegedly was home at the time of the party declined to comment when reached Friday.

According to the report, Ellis lost control of the Acura TSX along a curve on Dufief Mill Road. In documenting Ellis’s speed, police said the car was going at least 65 in a 35 mph zone when the car first left tire marks on the roadway, but they could not say how much more because of the car’s airborne trajectory and its collisions with trees and the fence.

Alexander Murk, 18, and Calvin Li, 18, both members of Wootton’s class of 2015, were killed. Ellis was hospitalized in critical condition and was later released. The passenger in the front seat was injured and provided details to police while at the hospital.

Ellis was found to have a blood alcohol level of 0.07 to 0.09, well above the 0.02 limit for drivers in Maryland who are younger than 21. According to hospital tests cited in the report, he also tested positive for marijuana and benzodiazepines, contained in commonly prescribed sedatives. The two passengers who died had blood alcohol levels of 0.13 and 0.11, according to the report.