Police said Thursday they were unsure how much money or whether anything else was taken from the house.
Sullivan's 22-year-old brother was hit in the face and suffered a cut during the attack, but his young niece, 30-year-old sister, and mother, who police said is in her 50s, were not physically harmed, investigators said.
In the aftermath of the crime, the wailing of relatives and friends who gathered on steps and corners filled the narrow block as police led the survivors to the steps of the two-story house.
Sullivan's sister's arms were wrapped tightly around the child.
Police whisked them away to be interviewed by homicide detectives, and investigators said they didn't think anyone saw the gunmen enter or leave the house. But a surveillance camera on the awning of a nearby corner store may have captured the men.
Small said the victims told police three to five masked men had committed the crime. He said duct tape and zip ties were found in the bedroom where Sullivan was slain and in the living room, along with a shell casing in the bedroom.
Investigators said they were unsure whether there were any signs of forced entry, and police said they were uncertain whether the victims knew their attackers.
Sullivan was convicted last year on an animal-cruelty charge involving two puppies with clipped ears and was fined, the PSPCA said.
Early Thursday, as police continued to investigate, disbelieving relatives held one another tightly, tears flowing.
A man who gave his name only as Cary and who identified himself as Sullivan's cousin looked on with a crowd of about 30 people - most of whom, he said, were other family members - at the end of the block.
"Right now, we're just trying to find out what happened," he said. "We're hurting."
Contact Morgan Zalot at 215-854-5928, firstname.lastname@example.org, or follow @morganzalot on Twitter. Read her blog at phillyconfidential.com.