An after-prom party near Black Point beach in Chilmark turned violent in the early morning hours last Sunday when police who were called in to break up the party tried arresting a teenager and were forced to retreat under a barrage of beer bottles.

Two police officers were injured, three teenagers arrested, and now, under a swirl of charges that police used excessive force, Chilmark police chief Tim Rich is promising to investigate the actions of police officers.

Of the teenagers arrested, one was charged with disorderly conduct, another with marijuana possession and a third with assault and battery, for allegedly spitting on a police officer.

The party was no small gathering. Police estimate that some 150 to 180 people, most of them teenagers, had driven down the long, bumpy Quansoo road and through what was supposed to be a locked gate to the beach parking lot. A bonfire got started and so did the drinking.

Three police officers arrived on the scene at about 2 a.m. after the beach caretaker, Larry Hepler, called in with a noise complaint. Chilmark officer Ryan Myett was in charge, and backing him up were Edgartown officer John Hanafin and Tisbury officer Robert Fiske. Both Mr. Myett and Mr. Hanafin, a part-time officer, have been on the force just one year. Mr. Fiske is a six-year veteran.

According to Chief Rich, most of the youths cooperated with police. Teenagers began to extinguish the fire by pouring beer on it, and as police asked for designated drivers to come forward and take a field sobriety test, the ranks of the party-goers began to thin.

"Most of the kids were very respectful," Chief Rich said. "They dispersed without incident. They understood the party was over, and they were prepared to leave."

But some of the teenagers from the party told a different story of what happened after police arrived. They said the police cursed at them, pepper sprayed bystanders and threatened to shoot when the situation got out of control.

Some 20 youths gathered Monday night at the Tisbury home of Donna Carroll, the mother of 18-year-old Matt Ritchie, who was arrested for disorderly conduct, and his brother, 19-year-old Zachary Ritchie, who claims he was beaten by police after he questioned the arrest of his brother. Listening to their side of the story was Tisbury attorney, Daniel Larkosh, who issued a scathing press release the next day, calling the police action "confrontational, abusive and disrespectful."

On Tuesday evening, six teenagers gathered for a press conference in Mr. Larkosh's office and recounted the events of early Sunday morning. High school junior Ellen Kildegaard said police began swearing at them the minute they came on the scene and gave confusing orders about what the teens were supposed to do.

"They gave sobriety tests to people, and they kept sober drivers in a corner," she said. "We didn't know if we were supposed to go or not."

The real trouble started, the teens said, when police zeroed in on Matt Ritchie. Police said he had kicked hay onto the fire, but Matt Ritchie claimed that all he did was kick a bale of hay out of frustration with the police. "I kicked the bale, and it moved a few inches," he said, adding that while other kids had tossed hay on the fire, the hay he kicked did not go into the fire.

When police moved in to arrest him and handcuff him, his brother Zachary protested. According to police reports, Zachary Ritchie, shoved one of the officers, but he would admit only to name-calling. "I might have called them a pig," he said. "But I didn't ever touch a police officer."

The next thing he remembers is being tackled by police officers. "I didn't do anything, and there were three police officers on me," he said. Pinned under them was Miss Kildegaard whose face was scraped and eye swollen by the impact.

Some of the teenagers watching this scene unfold then erupted, according to both the youths and the police reports filed by the three officers. Some began throwing bottles at the police, and others shouted obscenities. Police responded with pepper spray before backing off, having failed to place handcuffs on Zachary Ritchie.

None of the teenagers sought medical treatment at the hospital, and Mr. Larkosh said his goal is not to file suit against the police. Rather, he wants the police to examine what went wrong and take steps to prevent it from happening again.

"We'd like police to address this internally," he said, "and to make some acknowledgement of mistakes made. When officers approach this kind of scene, they need to do so with more sensitivity."

On the police side, Chief Rich called Sunday's events at the beach "an unfortunate incident."

"I take allegations of civil rights violations very seriously," said Chief Rich. "I have initiated a separate investigation to look into allegations made in [Mr. Larkosh's] press release."

But police accounts of the events offer another story. According to those reports, the officers were able to get more than half of the party-goers to leave the scene once they started the field sobriety tests.

But some of the teenagers, police said, were not cooperating with orders to put out the fire. Instead, some were intentionally throwing hay back on the fire to re-ignite it. Police said they then announced that anyone who threw flammable material back onto the bonfire would be arrested for disorderly conduct.

That's when they spotted Matt Ritchie kicking hay. Officer Fiske went to arrest him. According to reports, Zachary Ritchie then shoved the police officer as he walked by. The officer grabbed the young man, and the two fell to the ground. Officer Hanafin went to assist Mr. Fiske.

"A large crowd began to circle around us and shout obscenities. Zachery Ritchie was resisting arrest and subsequently was sprayed with O.C. [pepper spray]," according to Mr. Hanafin's report. "The angry crowd turned into a hostile mob . . . and were shouting ‘You pigs . . . Nazis' (and other obscenities). As the crowd surrounded us, they began spitting on us and throwing beer bottles and blocks of wood."

Officer Hanfin was hit both on the left side of his face and on his forearm as he tried to defend himself from the projectiles. Officer Myett, who had lost his flashlight, was then struck in the back of the head by a heavy object. Police suspect one of the youths used the three-pound flashlight as a weapon.

Taunted by members of the crowd, Mr. Hanafin pulled out his pepper spray and warned the youths to stay back. They continued their shouting, and according to the report, Officer Hanafin sprayed into the group. At this point, police engaged in what the chief called a tactical withdrawal, retreating back to their cruisers to call for all available police as backup.

Chief Rich said police from every Island town responded, bringing some dozen officers onto the scene by about 3 a.m.

Both sides agreed that what helped ease the tension was the ultimate presence of police who knew many of the teenagers through their work as school resource officers, namely West Tisbury Officer Brian Cioffi and Sgt. Dan Rossi.

"Brian Cioffi and Dan Rossi made everything calm down," said Althea Miller, one of the teenagers at Mr. Larkosh's press conference.

Sergeant Rossi said this week that the party was much larger than typical parties on the beach. He said there were also many party-goers who were not from the high school, young people who were as old as 21 or 22. "That doesn't mix well," he said.

By the time the dust settled, police had arrested not only Matt Ritchie, but also William Bailey Jr., 19, of Edgartown, charging him with possession of marijuana, and Tiffany Vanderhoop, for allegedly spitting on a police officer. Miss Vanderhoop, who came out on Tuesday to speak to the press, denied that she spit on police. She said she was spitting on the ground as she walked by police, telling them "You guys ought to be ashamed of yourselves."

While Chief Rich said he is encouraging people who are concerned about police behavior to come forward, he is also clearly distressed that some of the youths had lashed out so violently at police.

"I'm very much concerned. If someone hits a police officer, I don't care if you're intoxicated or not, the response from a police officer could end your life," he said. "I give the officers credit for backing off. This could have gotten a lot more nasty."

The party at Black Point beach was not the only party following the prom. Organizers of an alcohol-free party at the Boys' and Girls' Club said 137 high school students came out for a night of karaoke and cash giveaways that lasted until 5 a.m.

Drivers at the SafeRides program, operated by high school students, also stayed busy into the early morning hours of prom night, responding to 10 calls for a free ride home from a teen who was either in trouble or too intoxicated to drive.