It was close to 4 a.m. Friday when members of the Pennsylvania State Police crime unit arrived at the property, which straddles both Edgmont Township in Delaware County and Willistown Township in Chester County. O’Neill’s blood alcohol content was about .175 according to a preliminary breath test administered by a trooper.

O’Neill "made statements to authorities indicating he had killed Sheridan" and had told other friends who were at the house when the shooting occurred to leave, according to the affidavit of probable cause for arrest.

Witnesses told investigators O’Neill was pointing his father’s .45-caliber semi-automatic pistol equipped with a laser system at Sheridan and others who had attended a party at the O’Neill home.

"Sheridan attempted to knock the weapon away and it went off," the affidavit reads. Sheridan was shot in the face and pronounced dead at the scene. He would have been a senior at Cardinal O’Hara High School this year.

"Kids are devastated," said one West Chester resident, whose daughter graduated in June from O’Hara and was friendly with Sheridan.

Authorities said the shooting came at the end of an underage drinking party, which O’Neill was hosting Thursday night into Friday morning while his parents were at Sea Isle City, N.J., and his older sister was at work. Many individuals attended the party but as time wore on, the majority of partygoers departed, according to the document.

One of those in attendance told investigators the gun, which was stored between the mattress and box spring in O’Neill’s parents’ bedroom, was being "handled unsafely," so he left the party, according to the affidavit. He also said that at one point, O’Neill had pointed the gun at him.

Authorities were told O’Neill pulled the weapon out more than once during the party, including during a beer run O’Neill and others made to a Middletown Township bar. While in the car, O’Neill gave the gun to another person who then "shot the unoccupied vehicle of someone with whom the rest of the boys had a problem," the affidavit states.

By the end of the night, O’Neill, Sheridan and two others were alone when O’Neill got the gun and turned on the laser designator. O’Neill put the laser light on the three friends, who proceeded to duck behind a car. O’Neill dropped the gun to his side and the friends came out from behind the car. It was then that O’Neill raised the gun and pointed it at Sheridan and Sheridan knocked it away. The weapon went off and Sheridan collapsed in the driveway.

O’Neill was charged with involuntary manslaughter, aggravated assault, simple assault, reckless endangerment, tampering with evidence, purchase of liquor and weapons offenses, and remanded to Chester County prison.

Though his bail, 10 percent of $50,000, was posted, conditions including psychiatric and drug evaluations and home monitoring had not been met as of late Sunday.

A funeral Mass for Sheridan will be celebrated 11 a.m. Wednesday at SS. Simon and Jude Church.