"When I heard about it, I felt grief over my dad's killing and then I felt the grief for my uncle," said the victim's son and namesake, Robert Kaullar, 28.
The details surrounding his father's death were told to him by his aunt, who was there that night, he said.
About 3 a.m., Christopher, his wife and Robert were inside the VFW Post on Old Newtown Road near Bickley Street when the two men got into an argument over bikes, he said.
"It must have gotten personal because it escalated," he said.
The two stumbled outside, where they came to blows.
"Chris was on the ground and he started shooting," he said.
Robert Kaullar was shot in the left hand and side, police said. His sister-in-law was also shot, but was only grazed. Both were taken to Aria Health-Torresdale, where Robert Kaullar was pronounced dead at 8:26 p.m.
Christopher Kaullar has been charged with his murder, police said. His arraignment is scheduled for Wednesday.
The younger Robert Kaullar said he hopes that surveillance video from the building will help answer questions about the incident.
"It must have been a temporary act of rage," he said of his uncle. "He was out of character."
The two brothers may have taken different paths in life - one became a cop, the other a criminal - but they were tight, he said.
"They were each other's favorite siblings," he said. "He was my dad's baby brother."
While Christopher Kaullar - of Trout Road near Rising Sun Avenue, in the Northeast - was patrolling the streets of South Philly in the 3rd Police District, 11th and Wharton streets, his brother was serving a 19-year sentence for his involvement in the Roy Stocker gang, a Bucks County drug ring that allegedly had ties to organized crime.
The three other sons in the family all served time in prison, the younger Robert said.
Court records show Robert Kaullar's extensive criminal history dates from the '80s. Among his misdeeds, Kaullar, a former professional boxer profiled in the Daily News, was convicted of burglary and conspiracy.
The brothers did share some similarities. Both were motorcycle enthusiasts and enjoyed fishing together, said the younger Robert. His uncle worked as a printer after retiring from the Police Department about five years after joining in 2001. His father worked in construction.
Estranged from his father for most of his life, the younger Robert Kaullar said it was his uncle who stepped in to fill the void.
"He was a family man," he said of his uncle, a father of three small children. "He was the only one of my uncles who didn't do any prison time."
"He was there a lot for me. He would do stuff with me that my father would do. I'm disappointed that he killed my father, but I love him so much. I can't stop loving my uncle."
But Robert will also mourn his father, who he said had turned over a new leaf since being released from prison a few years ago.
"When he got out, he tried to turn his life around," he said. "He was no angel, but he was no longer a criminal."