She was found naked and face-down in a bathtub full of water, another police source said. Peruto told police he was in Avalon, N.J., when Law's body was found, the source said.
Richard L. DeSipio, an associate in Peruto's firm, said he received a frantic phone call from Peruto on Saturday morning shortly after his boss heard of the death.
Peruto called as he sped back from the Shore, DeSipio said.
"He was just devastated. He was just in hysterics," DeSipio, who described himself as a long-time friend of Peruto's, said in an interview Sunday. "I was afraid he was going to get into an accident."
DeSipio said he rushed to Peruto's house after the call and Law's body was still there when he arrived.
DeSipio said other colleagues at the firm were also upset.
A maintenance man found Law's body just after 10 a.m. Saturday, police said. She was pronounced dead shortly before 10:30 a.m.
Law described herself as working for the Peruto firm as a paralegal, according to her social-media profiles and friends.
In a Facebook posting, Peruto, 58, wrote: "I'm especially sad for her 10 yr old brother, who was her life, along with her loving and close sisters, mother and step-father. Earth lost the best one ever."
He added: "Happy birthday baby." Law would have turned 27 on Tuesday.
DeSipio said "everyone's been nonstop crying; every single one of us is horrified. We'll never be the same."
When Law's dog, Sophie, died about six months ago, she wept and had planned to plant a rose bush in her memory, DeSipio said.
Law also had a mischievous streak, DeSipio said, with an impish smile and uncanny ability to mimic others. He said he would remember her spot-on impressions of clients.
However, a colleague who spoke on condition of anonymity said Law had recently told some close friends about emotional turmoil.
A man who picked up the phone at the Absecon, N.J., home of one of Law's relatives declined to comment.
A spokeswoman for Philadelphia police Sunday said there were no other details to give out.
Contact Jonathan Lai at 856-779-3220, firstname.lastname@example.org, or follow on Twitter @elaijuh.
Inquirer staff writers Carolyn Davis and Allison Steele contributed to this article.