Spectators had been warned against outbursts, but the verdict from the Common Pleas Court jury of eight women and four men hit the packed courtroom like a seismic wave.
Karen Panas, mother of 21-year-old victim William "Billy" Panas Jr., let out a scream at the word guilty. She was echoed a split-second later by a louder shriek from Sheila Tepper.
"Oh, my God!" Tepper gasped, collapsing against the shoulders of a relative.
As the stunned, standing jurors watched from the box, deputy sheriffs began ordering members of the Tepper and Panas families to leave.
But Sheila Tepper seemed unable to stand or walk, and two relatives held her up and dragged her from the room as she screamed, "I'm going to be sick, I'm going to be sick!"
The Teppers' daughter, Felicia, who testified in her father's behalf during the seven-day trial, sat in the hall, screaming and flailing at relatives trying to calm her.
Frank Tepper, a former police civil affairs officer with the department for 16 years, stood surrounded by deputies as the room erupted.
Judge Shelley Robins New had intended to sentence Tepper immediately - common in first-degree murder verdicts, where the sentence is mandatory and carries no chance of parole.
But the courtroom commotion, and the Panas family's desire to make victim-impact statements, led her to postpone the formal sentencing hearing until March 29.
Outside the courthouse on Filbert Street, Panas' father said he would sue the city for his son's shooting, citing several incidents in which Tepper was investigated for drawing his firearm in public.
"They should have fired him in 1995," Panas said, referring to one of the incidents. "The city did nothing."
Panas praised the verdict, adding, "I hope he rots in hell, goes into general population, and never sees the light of day."
Holding his hands to the sky, Panas looked up and called out loudly to his son: "Billy P., I love you, man. I told you I got your back!"
Defense attorney Fortunato "Fred" Perri Jr. would not say if he would appeal.
"As I said from the beginning, in this sad tragedy there would be no winners and no losers," Perri added.
Assistant District Attorney Michael Barry said the verdict was justified because Tepper, who was off duty, was not being assaulted or threatened when he aimed his personal semiautomatic pistol at Panas and told him and his friends to "back up."
Panas, some witnesses testified, replied by yelling, "He's not going to shoot anybody," before Tepper fired once, hitting him in the chest.
"He was a police officer," Barry said afterward. "He knows what it means when you shoot somebody in the middle of the chest."
Barry said the verdict "sends a message that nobody is above the law in this city, whether you're a police officer or a doctor or a priest. . . . I think that's important."
The jury had to decide between first- or third-degree murder, or voluntary manslaughter.
First-degree murder is the most serious crime in Pennsylvania: the premeditated, malicious killing of another person.
The word premeditation carries a lay connotation of a long period of reflection. But New explained that under the law, premeditation can take a "fraction of a second."
It was the jury's duty to infer from the evidence - testimony, circumstances, and conduct - whether Tepper intended to kill Panas before he shot him shortly before 11 p.m. on Nov. 21, 2009, the judge added.
The shooting occurred during a baby shower the Teppers were throwing for their daughter, and the incident played out on 15-foot-wide Elkhart Street in Port Richmond, in front of Tepper's house.
Trial witnesses testified that about 10:30 p.m., some of Tepper's guests and young men from the neighborhood argued and began fighting.
Another guest urged Tepper to intervene. Tepper went outside, where he was quickly jumped and punched by a group involved in the melee.
Perri argued that Tepper shot in self-defense after being attacked.
But Barry maintained that Panas was not part of the group that attacked Tepper. Barry said Tepper shot Panas because he was humiliated and because Panas mocked him, daring him to shoot.
As trial witnesses described it, Panas was not among those who jumped Tepper. Panas and friends, witnesses said, came from the opposite direction, curious about the nearby melee.
But after arriving, witnesses said, Panas and several friends got involved in the fighting until Tepper drew his gun and ordered them to back away, only to be challenged verbally by Panas.
"His ego couldn't handle it," Barry said.
Contact staff writer Joseph A. Slobodzian at 215-854-2985, email@example.com, or @joeslobo on Twitter.