Mass at the Cathedral Basilica of Saints Peter and Paul started with a prayer for Pope Benedict XVI, who died at 95 years old.
"I wasn't especially surprised, but there was a sadness to the news, hearing the confirmation," said Velma Clark, a Catholic.
News of his death came after Pope Francis asked for prayers earlier this week for Benedict's health.
"I felt sad for him at first, but then I realized if we believe he entered the heavenly abodes, we should be very happy for him," said Calan Baniewicz from Fairmount.
Pope emeritus Benedict XVI dies
Tributes for the former pope have been coming in from around the world, including from President Joe Biden, who is Catholic. He said of the former pontiff, "He will be remembered as a renowned theologian, with a lifetime of devotion to the Church, guided by his principles and faith."
Archbishop Nelson Pérez paid tribute too.
"I met him personally and he was a gentle soul," said Pérez.
Pope Benedict was the first pontiff in 600 years to resign his position rather than hold office for his entire life. The move stunned the world in 2013.
His resignation came amid criticism of his handling of the clergy sex abuse scandal.
"I can hear my grandmother's voice in my head, what she would have said. She wasn't alive to see him resign, but she would have been very disappointed in the church and the Pope," said Aaron Treat from New York.
Archbishop Pérez called Benedict's resignation an act of unparalled selflessness and said he believes the Pope resigned for his own health.
"He did the most loving thing. He did the most loving thing, the most heroic thing, he stepped away so that someone could do that better," said Perez.
Archbishop Perez will hold a special mass for Pope Benedict at the Basilica tomorrow morning at 11 a.m.